Optical recording medium judgment device and optical recording medium judgment method

ABSTRACT

It is an object of the present invention to provide an apparatus for discriminating an optical recording medium which can reliably discriminate the kind of an optical recording medium even in the case where the optical recording medium to be discriminated is warped and formed with periodical undulation in the circumferential direction thereof.  
     The apparatus  10  for discriminating an optical recording medium according to the present invention includes a first electrode  11,  a second electrode  12,  a third electrode  13,  a fourth electrode  14,  an alternating current signal generation circuit  17  for applying an alternating current signal A to the first electrode  11  and the third electrode  13,  a detection circuit  18  for detecting the level of an alternating current signal B 1  appearing at the second electrode  12  and the level of an alternating current signal B 2  appearing at the fourth electrode  14,  a supporting mechanism  15  for supporting the first electrode  11  and the second electrode  12,  a supporting mechanism  16  for supporting the third electrode  13  and the fourth electrode  14,  a driving mechanism  33  for vertically moving the supporting mechanism  15,  a driving mechanism  34  for vertically moving the supporting mechanism  16,  and a control circuit  19  for controlling the operations of the alternating current signal generation circuit  17,  the detection circuit  18,  the driving mechanism  33  and the driving mechanism  34,  and a table  19   a  is provided in the control circuit  19.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for discriminating anoptical recording medium and a method for discriminating an opticalrecording medium, and particularly, to an apparatus for discriminatingan optical recording medium and a method for discriminating an opticalrecording medium which can reliably discriminate the kind of an opticalrecording medium.

DESCRIPTION OF THE PRIOR ART

Optical recording media such as the CD, DVD and the like have beenwidely used as recording media for recording digital data and compatibledrives capable of reproducing data recorded in different opticalrecording media such as the CD, DVD and the like or recording andreproducing data therein and therefrom have recently been activelydeveloped.

Particularly, next-generation type optical recording media having largedata recording capacity and an extremely high data transfer rate haverecently been actively developed and it is expected that the kinds ofoptical recording media will further increase.

In such a compatible drive, it is necessary to discriminate the kind ofan optical recording medium set therein but since the shapes of thesedifferent kinds of optical recording media are standardized, it isimpossible to discriminate the kind of an optical recording medium settherein based on the shape thereof.

Therefore, a compatible drive is generally constituted so as todiscriminate the kind of an optical recording medium set therein byactually projecting a laser beam onto the optical recording medium settherein and judging whether or not a normal signal can be reproduced.

For example, a compatible drive capable of reproducing data recorded inboth CD and DVD is constituted so that when a distance between a lightincidence plane and a recording layer (reflective layer) is measured byconducting focus searching and it is judged that the distance betweenthe light incidence plane and the recording layer (reflective layer) isabout 1.1 mm, a laser beam having a wavelength of 780 nm for a CD isselected and that when it is judged that the distance between the lightincidence plane and the recording layer (reflective layer) is about 0.6mm, a laser beam having a wavelength of 650 nm for a DVD is selected.

However, in the case of discriminating the kind of an optical recordingmedium by conducting focus searching in this manner, a long time isrequired for discriminating the kind of the optical recording medium anda long period is required between the time when the optical recordingmedium is set in the drive and the time when data can be actuallyrecorded in or reproduced from the optical recording medium.

Therefore, Japanese Patent Application Laid Open No. 10-143986 proposesa method for discriminating an optical recording medium by providing anelectrode in a tray of a drive and applying an alternating currentsignal to the electrode, thereby discriminating the kind of an opticalrecording medium placed on the tray.

However, in the method disclosed in Japanese Patent Application LaidOpen No. 10-143986, the discriminating accuracy is lowered as describedbelow when the optical recording medium to be discriminated is warped.

FIG. 25 shows a tray provided with an electrode for detection that isused in Japanese Patent Application Laid Open No. 10-143986, where FIG.25(a) is a schematic plan view thereof and FIG. 25(b) is a schematiccross-sectional view taken along a line E-E in FIG. 25(a).

As shown in FIGS. 25(a) and 25(b), the tray 1 includes a first settingportion la on which an optical recording medium having a diameter of 120mm is to be placed and a second setting portion 1 b which is provided ata central portion of the first setting portion 1 a and on which anoptical recording medium having a diameter of 80 mm is to be placed andelectrodes 2, 3 are provided in the second setting portion 1 b.

Further, a shoulder portion 4 a is provided on the outer circumferentialportion of the first setting portion 1 a so that when an opticalrecording medium having a diameter of 120 mm is placed on the tray 1,the optical recording medium is held on the shoulder portion 4 a.

Similarly, a shoulder portion 4 b is provided on the outercircumferential portion of the second setting portion 1 b so that whenan optical recording medium having a diameter of 80 mm is placed on thetray 1, the optical recording medium is held on the shoulder portion 4b.

Therefore, when an optical recording medium is placed on the tray 1, therecording surface of the optical recording medium (which in the case ofan optical recording medium having a diameter of 120 mm is a region inwhich data are recorded that corresponds to that of the light incidenceplane and has an inner diameter of 50 mm and an outer diameter of 117mm) is kept from being brought into direct contact with the tray 1,thereby preventing the recording surface of the optical recording mediumfrom being damaged.

FIG. 26 is a schematic cross-sectional view showing the state of anoptical recording medium having a diameter of 120 mm placed on the tray1, wherein FIG. 26(a) shows the state where the optical recording mediumis warped in one direction and FIG. 26(b) shows the state where theoptical recording medium is warped in the other direction. In FIGS.26(a) and (b), the warpage of the optical recording medium isexaggerated.

As apparent from FIGS. 26(a) and (b), in the case where an opticalrecording medium is warped in the one direction, distances between theelectrodes 2, 3 for detection provided in the tray 1 and a conductivelayer(s) such as a reflective layer included in the optical recordingmedium become longer than that in the case where the optical recordingmedium is not warped and, on the other hand, in the case where anoptical recording medium is warped in the other direction, the distancesbetween the electrodes 2, 3 for detection provided in the tray 1 and aconductive layer(s) such as a reflective layer included in the opticalrecording medium becomes shorter than that in the case where the opticalrecording medium is not warped. As a result, when an alternating currentsignal is applied to one of the electrodes 2, 3, the level of the signalobtained from the other electrode 2, 3 depends upon whether or not theoptical recording medium is warped and in which direction the opticalrecording medium is warped and, therefore, there arises a risk of thedecrease in discriminating accuracy.

Further, in the method disclosed in Japanese Patent Application LaidOpen No. 10-143986, the discriminating accuracy is lowered as describedbelow when there is undulation or the like on the optical recordingmedium to be discriminated in the circumferential direction thereof.

FIG. 27 is a schematic perspective view showing an optical recordingmedium formed with periodical undulation in the circumferentialdirection thereof. FIG. 28(a) is a schematic cross-sectional view takenalong a line C-C in FIG. 27 and FIG. 28(b) is a schematiccross-sectional view taken along a line D-D in FIG. 2.

As shown in FIG. 27, the optical recording medium 20 is formed with fourconvex portions 29 a and four concave portions 29 b in thecircumferential direction thereof and in FIGS. 27 and FIG. 28(a), theconvex portions 29 a and the concave portions 29 b are exaggerated.

In the case where the optical recording medium 20 is formed withperiodical undulation in the circumferential direction thereof in thismanner, the optical recording medium 20 is warped in one direction atone cross-section thereof (cross-section along the line C-C in FIG. 27)and is warped in the other direction at another cross-section(cross-section along the line D-D in FIG. 27). As a result, in the casewhere the optical recording medium 20 is placed on the tray 1 shown inFIG. 25, distances between the electrodes 2, 3 for detection andconductive layers such as a reflective layer included in the opticalrecording medium 20 greatly vary depending upon how the opticalrecording medium 20 is placed on the tray 1.

FIG. 29 is a schematic cross-sectional view showing the state where theoptical recording medium 20 is placed on the tray 1, where FIG. 29(a)shows the case where a line connecting the electrodes 2, 3 substantiallycoincides with the line C-C in FIG. 27 and FIG. 29(b) shows the casewhere a line connecting the electrodes 2, 3 substantially coincides withthe line D-D in FIG. 27. The cross-section corresponding to the concaveportion 29 b is indicated by a broken line in FIG. 29(a) and thecross-section corresponding to the convex portion 29 a is indicated by abroken line in FIG. 29(b).

As shown in FIG. 29(a), in the case where the electrodes 2, 3 arelocated so as to face the convex portion 29 a of the optical recordingmedium 20 placed on the tray 1, distances between the electrodes 2, 3for detection provided in the tray 1 and a conductive layer(s) such as areflective layer included in the optical recording medium become longerthan that in the case where the optical recording medium is not warpedand has no undulation and, on the other hand, as shown in FIG. 29(b), inthe case where the electrodes 2, 3 are located so as to face the concaveportion 29 b of the optical recording medium 20 placed on the tray 1,distances between the electrodes 2, 3 for detection provided in the tray1 and a conductive layer(s) such as a reflective layer included in theoptical recording medium become longer than in the case where theoptical recording medium is not warped and has no undulation but shorterin the case shown in FIG. 29(a). Therefore, when an alternating currentsignal is applied to one of the electrodes 2, 3, the level of a signalobtained from the other of the electrodes 2, 3 varies depending upon howthe optical recording medium 20 is placed on the tray 1 and it istherefore difficult to accurately discriminate the kind of the opticalrecording medium 20.

Although this problem is not so serious in the case of discriminating aCD, DVD or other optical recording media having different focusdistances, it becomes very serious in the case of discriminating opticalrecording media whose focus distances are the same.

In the case of discriminating optical recording media that differ littlein the distance between the light incidence plane and a conductive layersuch as a reflective layer, for example, in the case where a DVD inwhich data are to be recorded in one layer on one side and a DVD inwhich data are to be recorded in two layers on one side are to bediscriminated, the results of discrimination are greatly affected bychanges in detection signals caused by the warpage of the opticalrecording media.

It is particularly worthy of note that there are being developednext-generation type optical recording media constituted so as to beirradiated with a laser beam having a wavelength equal to or shorterthan 450 nm via a light transmission layer disposed opposite to asubstrate using an objective lens having a numerical aperture equal toor smaller than 0.7. It is therefore expected that a plurality kinds ofnext-generation type optical recording media that differ only slightlyin the thickness and material of the light transmission layers will comeinto practical use. In the case where these next-generation type opticalrecording media are discriminated using the method disclosed in JapanesePatent Application Laid Open No. 10-143986, the results of thediscrimination are very greatly affected by changes in detection signalscaused by warpage of the optical recording media and periodicalundulation formed thereon in the circumferential direction thereof.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide anapparatus for discriminating an optical recording medium and a methodfor discriminating an optical recording medium which can reliablydiscriminate the kind of an optical recording medium.

It is another object of the present invention to provide an apparatusfor discriminating an optical recording medium and a method fordiscriminating an optical recording medium which can reliablydiscriminate the kind of an optical recording medium even in the casewhere the optical recording medium to be discriminated is warped andformed with periodical undulation in the circumferential directionthereof.

It is a further object of the present invention to provide an apparatusfor discriminating an optical recording medium and a method fordiscriminating an optical recording medium constituted so as to beirradiated with a laser beam from a side opposite to a substrate, whichcan reliably discriminate the kind of an optical recording medium.

The above objects of the present invention can be accomplished by anapparatus for discriminating an optical recording medium comprising atleast a first dielectric layer, a second dielectric layer and aconductive layer formed between the first dielectric layer and thesecond dielectric layer, the apparatus for discriminating an opticalrecording medium comprising a first detecting section provided with anelectrode and disposable in the vicinity of a surface of the firstdielectric layer, a second detecting section provided with an electrodeand disposable in the vicinity of a surface of the second dielectriclayer and a signal applying means for applying a signal for detection tothe electrode of the first detecting section and the electrode of thesecond detecting section.

According to the present invention, since the kind of an opticalrecording medium is discriminated by locating the first detectingsection and the second detecting section in the vicinity of the surfacesof the first dielectric layer and the second dielectric layer of theoptical recording medium and applying a signal for detection to theelectrodes, it is possible to accurately discriminate the kind of anoptical recording medium even in the case where the optical recordingmedium is warped and formed with periodical undulation in thecircumferential direction thereof.

In this specification, the statement that the first detecting section isdisposable in the vicinity of the surface of the first dielectric layerincludes a case where the first detecting section can be disposed closeto the surface of the first dielectric layer and a case where the firstdetecting section can be disposed in contact with the surface of thefirst dielectric layer and the statement that the second detectingsection is disposable in the vicinity of the surface of the seconddielectric layer includes a case where the second detecting section canbe disposed close to the surface of the second dielectric layer and acase where the second detecting section can be disposed in contact withthe surface of the second dielectric layer.

In a preferred aspect of the present invention, the apparatus fordiscriminating an optical recording medium further comprises a drivingmeans for moving the first detection section to a position in thevicinity of the surface of the first dielectric layer and away from thesurface of the first dielectric layer and moving the second detectionsection to a position in the vicinity of the surface of the seconddielectric layer and away from the surface of the second dielectriclayer, the driving means being constituted so as to locate the firstdetecting section and the second detecting section at positions in thevicinity of the surfaces of the first dielectric layer and the seconddielectric layer where the first detecting section and the seconddetecting section do not face each other.

In a further preferred aspect of the present invention, the drivingmeans is constituted so as to simultaneously locate the first detectingsection and the second detecting section at positions in the vicinity ofthe surfaces of the first dielectric layer and the second dielectriclayer and the signal applying means is constituted so as tosimultaneously apply signals for detection to the electrode of the firstdetecting section and the electrode of the second detecting section.

According to this preferred aspect of the present invention, since thekind of an optical recording medium can be discriminated while the firstdetecting section and the second detecting section are simultaneouslylocated at positions in the vicinity of the surfaces of the firstdielectric layer and the second dielectric layer where the firstdetecting section and the second detecting section do not face eachother and signals for detection are simultaneously applied to theelectrode of the first detecting section and the electrode of the seconddetecting section, it is possible to quickly discriminate the kind of anoptical recording medium.

In a further preferred aspect of the present invention, the drivingmeans includes a first driving means for moving the first detectionsection to a position in the vicinity of the surface of the firstdielectric layer and away from the surface of the first dielectric layerand a second driving means for moving the second detection section to aposition in the vicinity of the surface of the second dielectric layerand away from the surface of the second dielectric layer.

In another preferred aspect of the present invention, the apparatus fordiscriminating an optical recording medium further comprises a drivingmeans for moving the first detection section to a position in thevicinity of the surface of the first dielectric layer and away from thesurface of the first dielectric layer and moving the second detectionsection to a position in the vicinity of the surface of the seconddielectric layer and away from the surface of the second dielectriclayer, the driving means being constituted so as to locate the firstdetecting section and the second detecting section at positions in thevicinity of the surfaces of the first dielectric layer and the seconddielectric layer where the first detecting section and the seconddetecting section face each other.

In a further preferred aspect of the present invention, the drivingmeans is constituted so as to move one of the first detecting sectionand the second detecting section to a position in the vicinity of one ofthe first dielectric layer and the second dielectric layer while keepingthe other of the first detecting section and the second detectingsection away from the other of the first dielectric layer and the seconddielectric layer and the signal applying means is constituted so as toselectively apply a signal for detection to one of the electrode of thefirst detecting section and the electrode of the second detectingsection.

In a further preferred aspect of the present invention, the drivingmeans is constituted as a single driving means.

According to this preferred aspect of the present invention, since thedriving means is constituted as a single driving means, it is possibleto reduce space required for mounting the driving means on a drive.

In a further preferred aspect of the present invention, the drivingmeans is constituted so as to bring the first detecting section intocontact with the surface of the first dielectric layer and bring thesecond detecting section into contact with the surface of the seconddielectric layer.

According to this preferred aspect of the present invention, since thedriving means is constituted so as to bring the first detecting sectioninto contact with the surface of the first dielectric layer and bringthe second detecting section into contact with the surface of the seconddielectric layer, it is possible to accurately discriminate the kind ofan optical recording medium.

In a preferred aspect of the present invention, at least one of thefirst detecting section and the second detecting section is disposed ona tray of a drive.

According to this preferred aspect of the present invention, since atleast one of the first detecting section and the second detectingsection is disposed on a tray of a drive, the kind of an opticalrecording medium can be discriminated immediately after the opticalrecording medium is placed on the tray of the drive and it is thereforepossible to shorten time required for recording data in or reproducingdata from the optical recording medium after the optical recordingmedium is set in the tray.

In a further preferred aspect of the present invention, at least one ofthe electrode of the first detecting section and the electrode of thesecond detecting section is disposed around a center of a tray of adrive on which the optical recording medium is to be placed oversubstantially 180 degrees.

According to this preferred aspect of the present invention, since theelectrode used for discriminating the kind of an optical recordingmedium is disposed around a center of a tray of a drive on which theoptical recording medium is to be placed over substantially 180degrees,, it is possible to accurately discriminate the kind of anoptical recording medium even in the case where the optical recordingmedium is warped and formed with periodical undulation in thecircumferential direction thereof.

In a further preferred aspect of the present invention, at least one ofthe electrode of the first detecting section and the electrode of thesecond detecting section includes a first electrode to which a signalfor detection is applied and a second electrode at which a signaldepending upon the kind of an optical recording medium appears inresponse to application of the signal for detection to the firstelectrode.

In a further preferred aspect of the present invention, the firstelectrode and the second electrode are disposed to be spaced from eachother and to form at least a part of a substantially annular portionaround the center of the tray.

In a further preferred aspect of the present invention, the firstelectrode and the second electrode are disposed to be spaced from eachother in a circumferential direction of the optical recording medium tobe placed on the tray and over substantially 180 degrees around thecenter of the tray.

In a further preferred aspect of the present invention, the firstelectrode and the second electrode are disposed to be spaced from eachother in a radial direction of the optical recording medium to be placedon the tray and over substantially 180 degrees around the center of thetray.

In a further preferred aspect of the present invention, the firstelectrode and the second electrode are disposed to be spaced from eachother in a radial direction of the optical recording medium to be placedon the tray and over substantially 360 degrees around the center of thetray.

In another preferred aspect of the present invention, at least one ofthe first detecting section and the second detecting section is disposedin a main body of a drive.

In a further preferred aspect of the present invention, at least one ofthe first detecting section and the second detecting section isconstituted by a shaft of a roller of a slot-loading mechanism.

The above objects of the present invention can be also accomplished by amethod for discriminating an optical recording medium comprising atleast a first dielectric layer, a second dielectric layer and aconductive layer formed between the first dielectric layer and thesecond dielectric layer, the method for discriminating an opticalrecording medium comprising steps of locating a first detecting sectionprovided with an electrode in the vicinity of a surface of the firstdielectric layer, applying a signal for detection to the electrode ofthe first detecting section, locating a second detecting sectionprovided with an electrode in the vicinity of a surface of the seconddielectric layer, and applying a signal for detection to the electrodeof the second detecting section, thereby discriminating the kind of theoptical recording medium.

According to the present invention, since the kind of an opticalrecording medium is discriminated by locating a first detecting sectionprovided with an electrode in the vicinity of a surface of the firstdielectric layer, applying a signal for detection to the electrode ofthe first detecting section, locating a second detecting sectionprovided with an electrode in the vicinity of a surface of the seconddielectric layer, and applying a signal for detection to the electrodeof the second detecting section, it is possible to accuratelydiscriminate the kind of an optical recording medium even in the casewhere the optical recording medium is warped and formed with periodicalundulation in the circumferential direction thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an apparatus for discriminating anoptical recording medium that is a preferred embodiment of the presentinvention.

FIG. 2 is a diagram showing the structure of a first detecting section,wherein FIG. 2(a) is a schematic perspective view showing a firstdetecting section and FIG. (b) is a schematic cross-sectional view takenalong a line A-A in FIG. 2(a).

FIG. 3 is a schematic cross-sectional view showing a main body of adrive into which an apparatus for discriminating an optical recordingmedium that is a preferred embodiment of the present invention isincorporated.

FIG. 4 is a set of schematic cross-sectional views showing various kindsof optical recording media, wherein FIG. 4(a) is a schematiccross-sectional view showing a CD type optical recording medium, FIG.4(b) is a schematic cross-sectional view showing a DVD type opticalrecording medium and FIG. 4(c) is a schematic cross-sectional viewshowing a next-generation type optical recording medium.

FIG. 5 is a flow chart of a method for discriminating an opticalrecording medium using an apparatus for discriminating an opticalrecording medium.

FIG. 6 is a schematic cross-sectional view showing the state where adetecting section of an apparatus for discriminating an opticalrecording medium is in contact with a light incidence plane of anoptical recording medium.

FIG. 7(a) is a diagram showing a circuit formed between a firstelectrode and a second electrode and FIG. 7(b) is a diagram showing acircuit formed between a third electrode and a fourth electrode.

FIG. 8 is a schematic cross-sectional view showing a main body of adrive into which an apparatus for discriminating an optical recordingmedium that is another preferred embodiment of the present invention isincorporated.

FIG. 9 is a schematic cross-sectional view showing a tray of a drive onwhich an apparatus for discriminating an optical recording medium thatis another preferred embodiment of the present invention is mounted,wherein FIG. 9(a) shows the state where a tray is discharged from a mainbody and FIG. 9(b) shows the state where the tray is accommodated in themain body.

FIG. 10 is a schematic longitudinal cross-sectional view showing anotherexample of a method for mounting an apparatus for discriminating anoptical recording medium on a drive and FIG. 10(b) is a schematiccross-sectional view taken along a line B-B in FIG. 10(a).

FIG. 11 is a schematic cross-sectional view taken along a line B-B inFIG. 10(a) and shows a further example of a method for mounting anapparatus for discriminating an optical recording medium on a drive.

FIG. 12 is a block diagram showing an apparatus for discriminating anoptical recording medium that is a further preferred embodiment of thepresent invention.

FIG. 13 is a schematic cross-sectional view showing a main body of adrive into which an apparatus for discriminating an optical recordingmedium shown in FIG. 12 is incorporated.

FIG. 14 is a schematic plan view showing a tray which can beaccommodated in and discharged from a main body of a drive into which anapparatus for discriminating an optical recording medium that is apreferred embodiment of the present invention is incorporated.

FIG. 15 is a schematic plan view showing a positional relationshipbetween an optical recording medium and a first electrode and a secondelectrode when the optical recording medium is placed on a tray shown inFIG. 14.

FIG. 16 a flow chart of a method for discriminating an optical recordingmedium using an apparatus for discriminating an optical recording mediumshown in FIGS. 12 to 14.

FIG. 17 is a schematic plan view showing a tray which can beaccommodated in and discharged from a main body of a drive into which anapparatus for discriminating an optical recording medium that is afurther preferred embodiment of the present invention is incorporated.

FIG. 18 is a schematic plan view showing a positional relationshipbetween an optical recording medium and a first electrode and a secondelectrode when the optical recording medium is placed on a tray shown inFIG. 17.

FIG. 19 is a schematic plan view showing a tray which can beaccommodated in and discharged from a main body of a drive into which anapparatus for discriminating an optical recording medium that is afurther preferred embodiment of the present invention is incorporated.

FIG. 20 is a schematic plan view showing a positional relationshipbetween an optical recording medium and a first electrode and a secondelectrode when the optical recording medium is placed on a tray shown inFIG. 19.

FIG. 21 is a schematic plan view showing a tray which can beaccommodated in and discharged from a main body of a drive into which anapparatus for discriminating an optical recording medium that is afurther preferred embodiment of the present invention is incorporated.

FIG. 22 is a schematic plan view showing a positional relationshipbetween an optical recording medium and a first electrode and a secondelectrode when the optical recording medium is placed on a tray shown inFIG. 21.

FIG. 23 is a schematic plan view showing a tray which can beaccommodated in and discharged from a main body of a drive into which anapparatus for discriminating an optical recording medium that is afurther preferred embodiment of the present invention is incorporatedand on which a spindle motor is mounted.

FIG. 24 is a schematic cross-sectional view showing the state where anoptical recording medium is placed on a tray, wherein FIG. 24(a) showsthe case where an optical recording medium formed with no periodicalundulation in the circumferential direction thereof is placed on thetray and FIGS. 24(b) and(c) shows the cases where an optical recordingmedium formed with a periodical undulation in the circumferentialdirection thereof is placed on the tray.

FIG. 25 shows a tray provided with an electrode for detection that isused in a conventional apparatus for discriminating an optical recordingmedium, where FIG. 25(a) is a schematic plan view thereof and FIG. 25(b)is a schematic cross-sectional view taken along a line E-E in FIG.25(a).

FIG. 26 is a schematic cross-sectional view showing the state of anoptical recording medium placed on a tray, wherein FIG. 26(a) shows thestate where the optical recording medium is warped in one direction andFIG. 26(b) shows the state where the optical recording medium is warpedin the other direction.

FIG. 27 is a schematic perspective view showing an optical recordingmedium formed with periodical undulation in the circumferentialdirection thereof.

FIG. 28(a) is a schematic cross-sectional view taken along a line C-C inFIG. 27 and FIG. 28(b) is a schematic cross-sectional view taken along aline D-D in FIG. 27.

FIG. 29 is a schematic cross-sectional view showing the state where anoptical recording medium is placed on a tray, wherein FIG. 29(a) showsthe case where a line connecting electrodes for detection substantiallycoincides with the line C-C in FIG. 27 and FIG. 29(b) shows the casewhere a line connecting the electrodes for detection substantiallycoincides with the line D-D in FIG. 27.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be describedwith reference to accompanying drawings.

FIG. 1 is a block diagram showing an apparatus for discriminating anoptical recording medium that is a preferred embodiment of the presentinvention.

As shown in FIG. 1, an apparatus 10 for discriminating an opticalrecording medium that is a preferred embodiment of the present inventionincludes a first electrode 11, a second electrode 12, a third electrode13, a fourth electrode 14, an alternating current signal generationcircuit 17 for applying an alternating current signal A to the firstelectrode 11 and the third electrode 13, a detection circuit 18 fordetecting the level of an alternating current signal B1 appearing at thesecond electrode 12 and the level of an alternating current signal B2appearing at the fourth electrode 14, a supporting mechanism 15 forsupporting the first electrode 11 and the second electrode 12, asupporting mechanism 16 for supporting the third electrode 13 and thefourth electrode 14, a driving mechanism 33 for vertically moving thesupporting mechanism 15, a driving mechanism 34 for vertically movingthe supporting mechanism 16, and a control circuit 19 for controllingthe operations of the alternating current signal generation circuit 17,the detection circuit 18, the driving mechanism 33 and the drivingmechanism 34. A table 19 a is provided in the control circuit 19.

As shown in FIG. 1, a first detecting section 31 is constituted by thefirst electrode 11, the second electrode 12 and the supporting mechanism15 for supporting the first electrode 11 and the second electrode 12 anda second detection section 32 is constituted by the third electrode 13,the fourth electrode 14 and the supporting mechanism 16 for supportingthe third electrode 13 and the fourth electrode 14.

FIG. 2 is a diagram showing the structure of the first detecting section31, wherein FIG. 2(a) is a schematic perspective view showing thedetecting section 31 and FIG. (b) is a schematic cross-sectional viewtaken along a line A-A in FIG. 2(a).

As shown in FIG. 2(a), the supporting mechanism 15 is constituted by anarm 15 a adapted to be vertically moved by the driving mechanism 33 anda plate-like electrode mounting section 15 b provided at the tip endportion of the arm 15 a.

The first electrode 11 and the second electrode 12 are mounted on theelectrode mounting section 15 b and, as shown in FIG. 2(b), the surfacesof the first electrode 11 and the second electrode 12 are covered with aprotective layer 35.

The protective layer 35 serves to prevent the first electrode 11 and thesecond electrode 12 from being corroded and also prevent the firstelectrode 11 and the second electrode 12 from coming into contact with arecording surface of an optical recording medium, thereby preventing therecording surface of the optical recording medium from being damaged bythe first electrode 11 and the second electrode 12.

Therefore, it is necessary for the protective layer 35 to be formed of amaterial having good moisture-resistant property, good surfacelubricating property, rubber elasticity, lower hardness than thatforming a recording surface of an optical recording medium, good heatresistant property, good chemical resistant property and good moldingproperty, and it is preferable to form the protective layer 35 ofthermoplastic polyether ester elastomer, silicon resin, fluorocarbonresin or the like.

Although not shown, the second detection section 32 has a similarstructure to that of the first detection section 31. Specifically, thesupporting mechanism 16 of the second detection section 32 isconstituted by an arm 16 a adapted to be vertically moved by the drivingmechanism 34 and a plate-like electrode mounting section 15 b providedat the tip end portion of the arm 16 a. The third electrode 13 and thefourth electrode 14 are mounted on the electrode mounting section 16 band the surfaces of the third electrode 13 and the fourth electrode 14are covered with a protective layer 35.

The apparatus 10 for discriminating an optical recording medium isadapted to be mounted on a data recording and reproducing apparatus forrecording data in and reproducing data from an optical recording mediumor a data reproducing apparatus for reproducing data from an opticalrecording medium (hereinafter collectively referred to as “a drive”).

FIG. 3 is a schematic cross-sectional view showing a main body of adrive into which an apparatus for discriminating an optical recordingmedium that is a preferred embodiment of the present invention isincorporated.

As shown in FIG. 3, when the tray 41 on which an optical recordingmedium 20 is placed is accommodated in the main body 40 of the drive,the thus constituted first detecting section 31 is located at a positionwhere it can be brought into contact with one surface of the opticalrecording medium 20 by actuating the driving mechanism 33 and the seconddetecting section 32 is located at a position where it can be broughtinto contact with the other surface of the optical recording medium 20by actuating the driving mechanism 34.

Further, as shown in FIG. 3, the first detecting section 31 and thesecond detecting section 31 are disposed so that they do not face eachother when the first detecting section 31 comes into contact with theone surface of the optical recording medium 20 and the second detectingsection 32 comes into contact with the other surface of the opticalrecording medium 20.

FIG. 4 is a set of schematic cross-sectional views showing various kindsof optical recording media, wherein FIG. 4(a) is a schematiccross-sectional view showing a CD type optical recording medium, FIG.4(b) is a schematic cross-sectional view showing a DVD type opticalrecording medium and FIG. 4(c) is a schematic cross-sectional viewshowing a next-generation type optical recording medium.

As shown in FIG. 4(a), a CD type optical recording medium 20 a includesa substrate 21 a, a recording layer 22 a formed on the substrate 21 a, areflective layer 23 a formed on the recording layer 22 a and aprotective layer 24 a formed on the reflective layer 23 a, and thecentral portion of thereof is formed with a hole 25 a. In the thusconstituted CD type optical recording medium 20 a, a laser beam L20 ahaving a wavelength λ of 780 nm is projected thereonto from the side ofthe substrate 21 a, thereby recording data therein and reproducingrecorded therein.

The substrate 21 a serves to ensure the mechanical strength required bythe optical recording medium 20 a and an optical path for a laser beamL20 a is formed therein.

In the case where the optical recording medium 20 a is to be constitutedas a write-once optical recording medium (CD-R) or a data rewritabletype optical recording medium (CD-RW), grooves and/or lands are formedon the surface of the substrate 21 a. The grooves and/or lands serve asa guide track for the laser beam L20 a when data are to be recorded orwhen data are to be reproduced.

The substrate 21 a has a thickness of about 1.1 mm and is normallyformed of polycarbonate resin.

In the case where the optical recording medium 20 a is to be constitutedas a write-once optical recording medium (CD-R) or a data rewritabletype optical recording medium (CD-RW), the recording layer 22 a isformed.

In the case where the optical recording medium 20 a is constituted as awrite-once optical recording medium (CD-R), the recording layer 22 a isformed of organic dye and in the case where the optical recording medium20 a is constituted as a data rewritable type optical recording medium(CD-RW), the recording layer 22 a is constituted by a phase change filmand dielectric films sandwiching the phase change film.

In a write-once type optical recording medium, data are recorded in therecording layer 22 a by transforming a predetermined region of organicdye contained in the recording layer 22 a. On the other hand, in a datarewritable type optical recording medium, data are recorded in therecording layer 22 a by changing the phase of the phase change filmcontained in the recording layer 22 a between a crystalline state and anamorphous state.

In the case where the optical recording medium 20 a is constituted as aROM type optical recording medium (CD-ROM), no recording layer 22 a isformed and data are recorded by pre-pits (not shown) formed on thesurface of the substrate 21 a when the optical recording medium 20 a isfabricated.

The reflective layer 23 a serves to reflect the laser beam L20 aentering via the substrate 21 a so as to emit it from the substrate 21 aand is formed so as to have a thickness of 10 to 300 nm.

The reflective layer 23 a is formed of metal such as aluminum, silver orthe like in order to effectively reflect the laser beam L20 a.

In this specification, a layer such as a reflective layer 23 a havingconductivity is sometimes referred to as “a conductive layer.” In thecase where the optical recording medium 20 a is constituted as a datarewritable type optical recording medium (CD-RW), since the material ofthe phase change film included in the recording layer 22 a normally hasconductivity, the recording layer 22 a falls in the category of “aconductive layer.”

The protective layer 24 a serves to physically and chemically protectthe recording layer 22 a. The protective layer 24 a is formed ofultraviolet ray curable resin or the like so as to have a thickness ofabout 100 μm.

In the thus constituted CD type optical recording medium 20 a, thedistance between the surface of the substrate 21 a through with thelaser beam L20 a enters and the reflective layer 23 a or the recordinglayer 22 a serving as a conductive layer is determined to be about 1.1mm.

On the other hand, as shown in FIG. 4(b), the DVD type optical recordingmedium 20 b includes a first substrate 21 b, a recording layer 22 bformed on the first substrate 21 b, a reflective layer 23 b formed onthe recording layer 22 b, an adhesive layer 28 b formed on thereflective layer 23 b and a second substrate 26 b formed on the adhesivelayer 28 b, and the central portion of thereof is formed with a hole 25b. In the thus constituted DVD type optical recording medium 20 b, alaser beam L20 b having a wavelength λ of 650 nm is projected thereontofrom the side of the first substrate 21 b, thereby recording datatherein and reproducing recorded therein.

The first substrate 21 b serves to ensure the mechanical strengthrequired by the optical recording medium 20 b and the optical path ofthe laser beam L20 b is formed therein.

In the case where the optical recording medium 20 b is to be constitutedas a write-once optical recording medium (DVD-R) or a data rewritabletype optical recording medium (DVD-RW), grooves and/or lands are formedon the surface of the first substrate 21 b. The grooves and/or landsserve as a guide track for the laser beam L20 b when data are to berecorded or when data are to be reproduced.

The second substrate 26 b corresponds to the protective layer 24 a inthe CD type optical recording medium 20 a.

Each of the first substrate 21 b and the second substrate 26 b has athickness of about 1.1 mm and is normally formed of polycarbonate resin.

The recording layer 22 b is formed in the case where the opticalrecording medium 20 b is to be constituted as a write-once opticalrecording medium (DVD-R) or a data rewritable type optical recordingmedium (DVD-RW).

In the case where the optical recording medium 20 b is constituted as awrite-once optical recording medium (DVD-R), the recording layer 22 b isformed of organic dye and in the case where the optical recording medium20 b is constituted as a data rewritable type optical recording medium(DVD-RW), the recording layer 22 b is constituted by a phase change filmand dielectric films sandwiching the phase change film.

In the case where the optical recording medium 20 b is constituted as aROM type optical recording medium (DVD-ROM), no recording layer 22 b isformed and data are recorded by pre-pits (not shown) formed on thesurface of the first substrate 21 b when the optical recording medium 20b is fabricated.

The reflective layer 23 b serves to reflect the laser beam L20 bentering via the first substrate 21 b so as to emit it from the firstsubstrate 21 b and is formed so as to have a thickness of 10 to 300 nm.

The reflective layer 23 b is formed of metal such as aluminum, silver orthe like in order to effectively reflect the laser beam L20 b.

In the thus constituted DVD type optical recording medium 20 b, thedistance between the surface of the first substrate 21 b through withthe laser beam L20 b enters and the reflective layer 23 b or therecording layer 22 b serving as a conductive layer is determined to beabout 0.6 mm.

Further, as shown in FIG. 4(c), the next-generation type opticalrecording medium 20 c includes a substrate 21 c, a reflective layer 23 cformed on the substrate 21 c, a recording layer 22 c formed on thereflective layer 23 c and a light transmission layer 27 c formed on therecording layer 22 c, and the central portion of thereof is formed witha hole 25 c. In the thus constituted next-generation type opticalrecording medium 20 c, a laser bream L20 c having a wavelength λ ofabout 400 nm is projected thereonto from the side of the lighttransmission layer 27 c located on the opposite side from the substrate21 c, thereby recording data therein and reproducing recorded therein.

The substrate 21 c serves to ensure the mechanical strength required forthe optical recording medium 20 c and in the case where the opticalrecording medium 20 c is to be constituted as a write-once opticalrecording medium or a data rewritable type optical recording medium,grooves and/or lands are formed on the surface of the substrate 21 c.

Unlike in the CD type optical recording medium 20 a and the DVD typeoptical recording medium 20 b, in the next-generation type opticalrecording medium 20 c, no optical path of the laser beam L20 c is formedin the substrate 21 c.

The substrate 21 c has a thickness of about 1.1 mm and is normallyformed of polycarbonate resin.

The reflective layer 23 c serves to reflect the laser beam L20 centering via the light transmission layer 27 c so as to emit it from thelight transmission layer 27 c and is formed so as to have a thickness of10 to 300 nm.

The reflective layer 23 c is formed of metal such as aluminum, silver orthe like in order to effectively reflect the laser beam L20 c.

The recording layer 22 c is formed in the case where the opticalrecording medium 20 c is to be constituted as a write-once opticalrecording medium or a data rewritable type optical recording medium.

In the case where the optical recording medium 20 c is constituted as aROM type optical recording medium, no recording layer 22 c is formed anddata are recorded by pre-pits (not shown) formed on the surface of thesubstrate 21 c when the optical recording medium 20 c is fabricated.

The light transmission layer 27 c is a layer in which the optical pathof the laser beam L20 c is formed.

Although the thickness of the light transmission layer 27 c depends uponthe kind of the next-generation type optical recording medium 20 c, thelight transmission layer 27 c is formed so as to have a thickness ofabout 10 to 300 μm.

Although the material preferably used for forming the light transmissionlayer 27 c depends upon the kind of the next-generation type opticalrecording medium 20 c, a dielectric material such as ultraviolet raycurable resin, polycarbonate, polyolefin or the like is normallyemployed.

Owing to the configuration of the next-generation type optical recordingmedium 20 c in the foregoing manner, in the case where thenext-generation type optical recording medium 20 c is constituted as aROM type optical recording medium or a write-once optical recordingmedium, the distance between the surface of the light transmission layer27 c through with the laser beam L20 c enters and the reflective layer23 c serving a conductive layer is determined to be about 10 to 300 μm.On the other hand, in the case where the next-generation type opticalrecording medium 20 c is constituted as a data rewritable type opticalrecording medium, the distance between the surface of the lighttransmission layer 27 c through with the laser beam L20 c enters and therecording layer 22 c which is a conductive layer closest to the lighttransmission layer 27 c is determined to be slightly shorter than thedistance between the surface of the light transmission layer 27 c andthe reflective layer 23 c.

The apparatus 10 for discriminating an optical recording medium shown inFIGS. 1 to 3 discriminates the kind of an optical recording medium 20among the optical recording media having different structures in theabove described manner as follows.

FIG. 5 is a flow chart of a method for discriminating an opticalrecording medium using the apparatus 10 for discriminating an opticalrecording medium.

In the case where the kind of an optical recording medium 20 is to bediscriminated using the apparatus 10 for discriminating an opticalrecording medium, the tray 41 of the drive is discharged from the mainbody 40 of the drive (Step S1) and an optical recording medium 20 isplaced on the tray 41 by the user (Step S2).

The tray 41 is then accommodated in the main body 40 of the drive (StepS3) and, correspondingly, the first detecting section 31 is moved upwardin FIG. 3 by the driving mechanism 33 under the control of the controlcircuit 19 until the protective layer 35 comes into contact with thelight incidence plane of the optical recording medium 20 andsimultaneously, the second detecting section 32 is moved downward inFIG. 3 by the driving mechanism 34 under the control of the controlcircuit 19 until the protective layer 35 comes into contact with thesurface opposite to the light incidence plane of the optical recordingmedium 20 (hereinafter referred to as a “reverse surface”) (Step S4).

As a result, as shown in FIG. 6, when the first detecting section 31 hascome into contact with the light incidence plane of the opticalrecording medium 20, substantially only the protective layer 35 isinterposed between the light incidence plane of the optical recordingmedium 20, and the first electrode 11 and the second electrode 12.

Therefore, in the case where the optical recording medium 20 placed onthe tray 41 is a CD type optical recording medium 20 a, the distancebetween the first electrode 11 and second electrode 12 and thereflective layer 23 or recording layer 22, which is a conductive layer,becomes equal to (1.1 mm+thickness of the protective layer 35) and inthe case where the optical recording medium 20 placed on the tray 41 isa DVD type optical recording medium 20 b, the distance between the firstelectrode 11 and second electrode 12 and the reflective layer 23 orrecording layer 22, which is a conductive layer, becomes equal to (0.6mm+thickness of the protective layer 35).

On the other hand, in the case where the optical recording medium 20placed on the tray 41 is a next-generation type optical recording medium20 c, the distance between the first electrode 11 and second electrode12 and the reflective layer 23 or recording layer 22, which is aconductive layer, becomes equal to (10 to 300 μm+thickness of theprotective layer 35).

Although not shown, when the second detecting section 32 comes intocontact with the reverse surface of the optical recording medium 20,substantially only the protective layer 35 is interposed between thereverse surface of the optical recording medium 20, and the thirdelectrode 13 and the fourth electrode 14.

Therefore, distances between the third electrode 13 and fourth electrode14 and the reflective layer 23, which is a conductive layer, depend uponthe kind of the optical recording medium 20.

In this embodiment, since the surface of the protective layer 35 hasgood lubricating property, the light incidence plane and the reversesurface of the optical recording medium 20 is not damaged when theprotective layer 35 comes into contact with the light incidence planeand the reverse surface of the optical recording medium 20.

When the first detecting section 31 comes into contact with the lightincidence plane of the optical recording medium 20 in this manner, acircuit shown in FIG. 7(a) is formed between the first electrode 11 andthe second electrode 12.

In FIG. 7(a), C1 is a capacitance component constituted by the firstelectrode 11, the reflective layer 23 or the recording layer 22 and adielectric material present between the first electrode 11 and thereflective layer 23 or the recording layer 22, and C2 is a capacitancecomponent constituted by the second electrode 12, the reflective layer23 or the recording layer 22 and a dielectric material present betweenthe second electrode 12 and the reflective layer 23 or the recordinglayer 22. Here, C1=C2.

Therefore, the values of the capacitance components C1 and C2 aredetermined depending upon the thickness and dielectric constant of thedielectric material present between the first electrode 11 and secondelectrode 12 and the reflective layer 23 or recording layer 22. In thecase where the optical recording medium 20 placed on the tray 41 isconstituted as a CD type optical recording medium 20 a, they becomeequal to Ca1 and in the case where the optical recording medium 20placed on the tray 41 is constituted as a DVD type optical recordingmedium 20 b, they become equal to Cb1, where Cb1 is larger than Ca1. Onthe other hand, in the case where the optical recording medium 20 placedon the tray 41 is constituted as a next-generation type opticalrecording medium 20 c, they become equal to Cc1, where Cc1 is largerthan Cb1.

Similarly, when the second detecting section 32 comes into contact withthe reverse surface of the optical recording medium 20, a circuit shownin FIG. 7(b) is formed between the third electrode 13 and the fourthelectrode 14.

In FIG. 7(b), C3 is a capacitance component constituted by the thirdelectrode 13, the reflective layer 23 and a dielectric material presentbetween the third electrode 13 and the reflective layer 23, and C4 is acapacitance component constituted by the fourth electrode 14, thereflective layer 23 and a dielectric material present between the fourthelectrode 14 and the reflective layer 23. Here, C3=C4.

Therefore, the values of the capacitance components C3 and C4 aredetermined depending upon the thickness and dielectric constant of thedielectric material present between the third electrode 13 and fourthelectrode 14 and the reflective layer 23. In the case where the opticalrecording medium 20 placed on the tray 41 is constituted as a CD typeoptical recording medium 20 a, they become equal to Ca2 and in the casewhere the optical recording medium 20 placed on the tray 41 isconstituted as a DVD type optical recording medium 20 b, they becomeequal to Cb2, where Cb2 is smaller than Ca2. On the other hand, in thecase where the optical recording medium 20 placed on the tray 41 isconstituted as a next-generation type optical recording medium 20 c,they become equal to Cc2, where Cc2 is smaller than Cb2.

Then, alternating current signals A generated by the alternating currentsignal generation circuit 17 are applied to the first electrode 11 andthe third electrode 13 under the control of the control circuit 19 whilethe first detecting section 31 is in contact with the light incidenceplane of the optical recording medium 20 and the second detectingsection 32 is in contact with the reverse surface of the opticalrecording medium 20 (Step S5).

As a result, since the alternating current signal A applied to the firstelectrode 11 is transmitted to the second electrode 12 via the circuitshown in FIG. 7(a) and the alternating current signal A applied to thethird electrode 13 is transmitted to the fourth electrode 14 via thecircuit shown in FIG. 7(b), an alternating current signal B1 appearingat the second electrode 12 varies depending upon the values of thecapacitance components C1 and C2 and an alternating current signal B2appearing at the fourth electrode 14 varies depending upon the values ofthe capacitance components C3 and C4.

As shown in FIG. 3, in this embodiment, when the first detecting section31 comes into contact with the light incidence plane of the opticalrecording medium 20 and the second detecting section 32 comes intocontact with the reverse surface of the optical recording medium 20,since the first detecting section 31 and the second detecting section 32do not face each other, the alternating current signal B1 appearing atthe second electrode 12 is not influenced by the alternating currentsignal A applied to the third electrode 13 and the alternating currentsignal B2 appearing at the fourth electrode 14 is not influenced by thealternating current signal A applied to the first electrode 11.

The alternating current signal B1 appearing at the second electrode 12and the alternating current signal B2 appearing at the fourth electrode14 are detected by the detection circuit 18 and the control circuit 19discriminates the kind of the optical recording medium 20 placed on thetray 41 based on the alternating current signal B1 and the alternatingcurrent signal B2 detected by the detection circuit 18 (Step S6).

More specifically, in the case where the level of the alternatingcurrent signal B1 is equal to that obtained when the values of thecapacitance components C1 and C2 are equal to Ca1 and the level of thealternating current signal B2 is equal to that obtained when the valuesof the capacitance components C3 and C4 are equal to Ca2, the controlcircuit 19 discriminates that the optical recording medium 20 placed onthe tray 41 is a CD type optical recording medium 20 a, and in the casewhere the level of the alternating current signal B1 is equal to thatobtained when the values of the capacitance components C1 and C2 areequal to Cb1 and the level of the alternating current signal B2 is equalto that obtained when the values of the capacitance components C3 and C4are equal to Cb2, the control circuit 19 discriminates that the opticalrecording medium 20 placed on the tray 41 is a DVD type opticalrecording medium 20 b. On the other hand, in the case where the level ofthe alternating current signal B1 is equal to that obtained when thevalues of the capacitance components C1 and C2 are equal to Cc1 and thelevel of the alternating current signal B2 is equal to that obtainedwhen the values of the capacitance components C3 and C4 are equal toCc2, the control circuit 19 discriminates that the optical recordingmedium 20 placed on the tray 41 is a next-generation type opticalrecording medium 20 c.

Therefore, if the range of the level of the alternating current signalB1 to be obtained and the range of the level of the alternating currentsignal B2 to be obtained are obtained in advance for each kind of theoptical recording media 20 and stored as a table 19 a in the controlcircuit 19, the kind of optical recording media 20 can be discriminatedby referring to the table 19 a in the control circuit 19.

When the discrimination of the kind of the optical recording medium 20has been completed, the first detecting section 31 is moved downward inFIG. 3 by the driving mechanism 33 and the second detecting section 32is moved upward in FIG. 3 by the driving mechanism 34 under the controlof the control circuit 19 so that the first detecting section 31 ismoved away from the light incidence plane of the optical recordingmedium 20 and the second detection section 32 is moved away from thereverse surface of the optical recording medium 20 (Step S7).

Thereafter, the optical recording medium 20 is rotated by a spindlemotor (not shown) (Step S8) and a laser component and an optical systemcorresponding to the kind of the optical recording medium 20discriminated at Step S6 are selected, thereby emitting a laser beam(Step S9).

Then, an initial setting operation and the like are effected similarlyto in the conventional drive and data are recorded in the opticalrecording medium 20 or data are reproduced from the optical recordingmedium 20.

Therefore, if the apparatus for discriminating an optical recordingmedium according to this embodiment is mounted on a drive, it ispossible to immediately discriminate the kind of an optical recordingmedium 20 set in the data recording and reproducing apparatus prior toprojecting a laser beam thereon.

According to this embodiment, since the kind of an optical recordingmedium is discriminated while the first detecting section 31 is incontact with the surface of the optical recording medium 20 and thesecond detecting section 32 is in contact with the reverse surface ofthe optical recording medium 20, even in the case where an opticalrecording medium 20 to be discriminated is warped and formed withperiodical undulation in the circumferential direction thereof, it ispossible to accurately discriminate the kind of the optical recordingmedium 20 without being affected by the warpage and periodicalcircumferential undulation of the optical recording medium 20.

Further, according to this embodiment, since the kind of an opticalrecording medium 20 is discriminated using the first detecting section31 from the side of the light incidence plane of the optical recordingmedium 20 and simultaneously, the kind of an optical recording medium 20is discriminated using the second detecting section 32 from the side ofthe reverse surface of the optical recording medium 20, it is possibleto more accurately discriminate the kind of an optical recording medium20 than in the case where the kind of an optical recording medium 20 isdiscriminated from only one side of an optical recording medium 20.

Therefore, according to this embodiment, even in the case where changein a detection signal caused by the warpage of an optical recordingmedium greatly affects the results of discrimination of the kind of anoptical recording medium 20 such as when discriminating a DVD in whichdata are to be recorded in one layer on one side and a DVD in which dataare to be recorded in two layers on one side, in which DVDs thedifference in distance between the light incidence plane and aconductive layers such as a reflective layer is small, the kind of theoptical recording medium 20 can nevertheless be accuratelydiscriminated.

Furthermore, according to this embodiment, since the kind of the opticalrecording medium 20 is discriminated by applying the alternating currentsignal A generated by the alternating current signal generation circuit17 to the first electrode 11 and detecting an alternating current signalB1 appearing at the second electrode 12 while the first detectingsection 31 is in contact with the surface of the optical recordingmedium 20, and applying the alternating current signal A generated bythe alternating current signal generation circuit 17 to the thirdelectrode 13 and detecting an alternating current signal B2 appearing atthe fourth electrode 14 while the second detecting section 32 is incontact with the reverse surface of the optical recording medium 20,even in the case of discriminating the kinds of next-generation typeoptical recording media that differ only slightly in the thickness andmaterial of the light transmission layers 27 c so that the values of thecapacitance components Cc1 and Cc2 are close to each other, thediscrimination can be made without being affected by an air layer havinga high dielectric constant. Therefore, it is possible to accuratelydiscriminate the kind of a next-generation type optical recording medium20 by detecting the level of the alternating current signal B1 appearingat the second electrode 12 and the level of the alternating currentsignal B2 appearing at the fourth electrode 14.

Moreover, according to this embodiment, since the first electrode 11,the second electrode 12, the third electrode 13 and the fourth electrode14 are each covered with the protective layer 35 having a goodlubricating property, it is possible to reliably prevent damage to thelight incidence plane of an optical recording medium 20 despite the factthat the protective layer 35 comes into contact with the light incidenceplane of the optical recording medium 20.

Further, according to this embodiment, since the first detecting section31 is moved away from the light incidence plane of the optical recordingmedium 20 by the driving mechanism 33 and the second detecting section32 is moved away from the reverse surface of the optical recordingmedium 20 by the driving mechanism 34 after discriminating the kind ofthe optical recording medium 20 and prior to rotation of the opticalrecording medium 20 by the spindle motor, it is possible to reliablyprevent the first detecting section 31 and/or the second detectingsection 32 from coming into contact with the light incidence planeand/or the reverse surface of the optical recording medium 20 anddamaging the optical recording medium 20 when the optical recordingmedium 20 is being rotated.

Furthermore, according to this embodiment, since the first detectingsection 31 and the second detection section 32 do not face each otherwhen the first detecting section 31 comes into contact with the lightincidence plane of the optical recording medium 20 and the seconddetecting section 32 comes into contact with the reverse surface of theoptical recording medium 20, the alternating current signal B1 appearingat the second electrode 12 is not influenced by the alternating currentsignal A applied to the third electrode 13 and the alternating currentsignal B2 appearing at the fourth electrode 14 is not influenced by thealternating current signal A applied to the first electrode 11.Therefore, since the kind of the optical recording medium 20 can bediscriminated simultaneously using the first detecting section 31 andthe second detection section 32, it is possible to shorten time requiredfor discriminating the kind of the optical recording medium 20.

FIG. 8 is a schematic cross-sectional view showing the main body of adrive into which an apparatus for discriminating an optical recordingmedium that is another preferred embodiment of the present invention isincorporated.

As shown in FIG. 8, in this embodiment, a first detecting section 31 anda second detecting section 32 of the apparatus 10 for discriminating anoptical recording medium are disposed on opposite sides with respect toan optical recording medium 20 to be discriminated and aresimultaneously driven by a common driving mechanism.

More specifically, when the kind of an optical recording medium 20 isdiscriminated using the first detecting section 31, the first detectingsection 31 is moved upward by the driving mechanism until the firstdetecting section 31 comes into contact with the light incidence planeof the optical recording medium 20.

As a result, the second detecting section 32 is also move upward andwhen the first detecting section 31 comes into contact with the lightincidence plane of the optical recording medium 20, the second detectingsection 32 is located to be spaced from the reverse surface of theoptical recording medium 20.

When the first detecting section 31 comes into contact with the lightincidence plane of the optical recording medium 20, the drivingmechanism is stopped, thereby keeping the first detecting section 31 atthat position and an alternating current signal A generated by thealternating current signal generation circuit 17 is applied to the firstelectrode 11 under the control of the control circuit 19.

As a result, the alternating current signal A applied to the firstelectrode 11 is transmitted to the second electrode 12 via the circuitshown in FIG. 7(a) and therefore, an alternating current signal B1appearing at the second electrode 12 varies depending upon the values ofthe capacitance components C1 and C2.

The alternating current signal B1 appearing at the second electrode 12is detected by the detection circuit 18 and the control circuit 19discriminates the kind of the optical recording medium 20 placed on thetray 41 based on the alternating current signal B1 detected by thedetection circuit 18.

When the discrimination of the kind of the optical recording medium 20using the first detecting section 31 has been completed, the drivingmechanism is operated and the second detecting section 32 is moveddownward until the second detecting section 32 comes into contact withthe reverse surface of the optical recording medium 20.

As the second detecting section 32 is moved downward, the firstdetecting section 31 is moved downward and moved away from the lightincidence plane of the optical recording medium 20.

When the second detecting section 32 comes into contact with the reversesurface of the optical recording medium 20, the driving mechanism isstopped, thereby keeping the second detecting section 32 at thatposition and an alternating current signal A generated by thealternating current signal generation circuit 17 is applied to the thirdelectrode 13 under the control of the control circuit 19.

As a result, the alternating current signal A applied to the thirdelectrode 13 is transmitted to the fourth electrode 14 via the circuitshown in FIG. 7(b) and therefore, an alternating current signal B2appearing at the fourth electrode 14 varies depending upon the values ofthe capacitance components C3 and C4.

The alternating current signal B2 appearing at the fourth electrode 14is detected by the detection circuit 18 and the control circuit 19discriminates the kind of the optical recording medium 20 placed on thetray 41 based on the alternating current signal B2 detected by thedetection circuit 18.

When the discrimination of the kind of the optical recording medium 20using the second detecting section 32 has been completed, the drivingmechanism is operated to move the first detecting section 31 and thesecond detecting section 32 upward and move the second detecting section32 away from the reverse surface of the optical recording medium 20, andthe driving mechanism is stopped so that the first detecting section 31and the second detecting section 32 are located away from the opticalrecording medium 20.

According to this embodiment, since the first detecting section 31 andthe second detecting section 32 are disposed on the opposite sides withrespect to an optical recording medium 20 to be discriminated and aresimultaneously driven by the common driving mechanism, it is possiblereduce space required for mounting the apparatus 10 for discriminatingan optical recording medium 20.

FIG. 9 is a schematic cross-sectional view showing a tray of a drive onwhich an apparatus for discriminating an optical recording medium thatis another preferred embodiment of the present invention is mounted,wherein FIG. 9(a) shows the state where a tray is discharged from a mainbody and FIG. 9(b) shows the state where the tray is accommodated in themain body.

In this embodiment, when a tray 41 is discharged from the main body 40of a drive, as shown in FIG. 9(a), a first detecting section 31 is movedto a position where it comes into contact with the light incidence planeof an optical recording medium 20 and on the other hand, when the tray41 is mounted in the main body 40, as shown in FIG. 9(b), the firstdetecting section 31 is moved away from the light incidence plane of anoptical recording medium 20.

Therefore, since the kind of an optical recording medium 20 can bediscriminated after placing the optical recording medium 20 on the tray41 and prior to accommodating the tray 41 in the main body 40 of thedrive by mounting the apparatus 10 for discriminating an opticalrecording medium on the drive in this manner, the time required forrecording data in or reproducing data from the optical recording medium20 after it is placed on the tray 41 can be considerably shortened.

FIG. 10 is a schematic longitudinal cross-sectional view showing anotherexample of a method for mounting an apparatus for discriminating anoptical recording medium on a drive and FIG. 10(b) is a schematiccross-sectional view taken along a line B-B in FIG. 10(a).

In this embodiment, a first electrode 11 and a second electrode 12 areconstituted by a shaft of one roller 53 of a slot-loading type drive anda third electrode 13 and a fourth electrode 14 are constituted by ashaft of the other roller 54 thereof.

Thus in this embodiment the one roller 53 constitutes a first detectingsection 31 and the other roller 54 constitutes a second detectingsection 32 so that, as shown in FIG. 10(b), the position of a gap 55between the first electrode 11 and the second electrode 12 coincideswith the position of a gap 56 between the third electrode 13 and thefourth electrode 14. Therefore, in the case where alternating currentsignals A are simultaneously applied to the first electrode 11 of thefirst detecting section 31 and the third electrode 13 of the seconddetecting section 32, an alternating current signal B1 appearing at thesecond electrode 12 is liable to be influenced by the alternatingcurrent signal A applied to the third electrode 13 and an alternatingcurrent signal B2 appearing at the fourth electrode 14 is liable to beinfluenced by the alternating current signal A applied to the firstelectrode 11.

Therefore, in this embodiment, the kind of an optical recording medium20 is discriminated by applying an alternating current signal A to thefirst electrode 11 or the third electrode 13 and detecting analternating current signal B1 appearing at the second electrode 12 or analternating current signal B2 appearing at the fourth electrode 14 andthen, the kind of an optical recording medium 20 is furtherdiscriminated by applying an alternating current signal A to the thirdelectrode 13 or the first electrode 11 and detecting an alternatingcurrent signal B2 appearing at the fourth electrode 14 or an alternatingcurrent signal B1 appearing at the second electrode 12.

FIG. 11 is a schematic cross-sectional view taken along a line B-B inFIG. 10(a) and shows a further example of a method for mounting anapparatus for discriminating an optical recording medium on a drive.

In this embodiment, a first electrode 11 and a second electrode 12 areconstituted by a shaft of one roller 53 of a slot-loading type drive anda third electrode 13 and a fourth electrode 14 are constituted by ashaft of the other roller 54 thereof. However, as shown in FIG. 11, inthis embodiment, the position of a gap 55 between the first electrode 11and the second electrode 12 is offset from the position of a gap 56between the third electrode 13 and the fourth electrode 14.

Therefore, even in the case where alternating current signals A aresimultaneously applied to the first electrode 11 of the first detectingsection 31 and the third electrode 13 of the second detecting section32, there is no risk of an alternating current signal B1 appearing atthe second electrode 12 being influenced by the alternating currentsignal A applied to the third electrode 13 and an alternating currentsignal B2 appearing at the fourth electrode 14 being influenced by thealternating current signal A applied to the first electrode 11.Therefore, in this embodiment, the kind of an optical recording medium20 can be discriminated by simultaneously applying alternating signals Ato the first electrode 11 of the first detecting section 31 and thethird electrode 13 of the second detecting section 32 and detecting thealternating current signal B1 appearing at the second electrode 12 andthe alternating current signal B2 appearing at the fourth electrode 14.

FIG. 12 is a block diagram showing an apparatus for discriminating anoptical recording medium that is a further preferred embodiment of thepresent invention.

As shown in FIG. 12, the apparatus 50 for discriminating an opticalrecording medium according to this embodiment includes a first electrode11, a second electrode 12, a third electrode 13, a fourth electrode 14,an alternating current signal generation circuit 17 for applying analternating current signal A to the first electrode 11 and the thirdelectrode 13, a detection circuit 18 for detecting the level of analternating current signal B1 appearing at the second electrode 12 andthe level of an alternating current signal B2 appearing at the fourthelectrode 14, and a control circuit 19 for controlling the operations ofthe alternating current signal generation circuit 17 and the detectioncircuit 18, and a table 19 a is provided in the control circuit 19.

As shown in FIG. 12, a first detecting section 51 is constituted by thefirst electrode 11 and the second electrode 12, and a second detectionsection 52 is constituted by the third electrode 13 and the fourthelectrode 14.

FIG. 13 is a schematic cross-sectional view showing a main body of adrive into which the apparatus 50 for discriminating an opticalrecording medium shown in FIG. 12 is incorporated.

As shown in FIG. 13, the first detecting section 51 constituted by thefirst electrode 11 and the second electrode 12 is mounted on a tray 41and the second detecting section 52 constituted by the third electrode13 and the fourth electrode 14 is mounted on the main body 40 of adrive.

As shown in FIG. 13, the second detecting section 52 is mounted on themain body 40 of the drive so as to cover an optical recording medium 20when the tray 41 on which the optical recording medium 20 is placed isaccommodated in the main body 40 of the drive.

FIG. 14 is a schematic plan view showing the tray which can beaccommodated in and discharged from the main body of the drive intowhich an apparatus for discriminating an optical recording medium thatis a preferred embodiment of the present invention is incorporated.

As shown in FIG. 14, the tray 41 which can be accommodated in anddischarged from the main body 40 of the drive includes an opticalrecording medium setting section 41 a on which an optical recordingmedium can be placed, and an opening 41 b formed in a central portion ofthe optical recording medium setting section 41 a and adapted forallowing a is spindle motor to chuck an optical recording medium whenthe tray 41 is accommodated in the main body 40 of the drive.

A shoulder portion 44 is provided on an outer circumferential portion ofthe optical recording medium setting section 41 a so that an opticalrecording medium is held by the shoulder portion 44 when it is placed onthe optical recording medium setting section 41 a of the tray 41.Therefore, when an optical recording medium is placed on the opticalrecording medium setting section 41 a of the tray 41, the recordingsurface of the optical recording medium is kept from being brought intodirect contact with the tray 1, thereby preventing the recording surfaceof the optical recording medium from being damaged.

As shown in FIG. 14, a first electrode 11 and a second electrode 12 areformed annular-like on the optical recording medium setting section 41 ain the vicinity of the shoulder portion 44. Each of the first electrode11 and the second electrode 12 forms substantially a half of the annularportion and gaps 42 and 43 are formed between the first electrode 11 andthe second electrode 12.

FIG. 15 is a schematic plan view showing a positional relationshipbetween an optical recording medium 20 and the first electrode 11 andthe second electrode 12 when the optical recording medium 20 is placedon the tray 41 shown in FIG. 14.

As shown in FIG. 15, when an optical recording medium 20 is placed onthe tray 41, the first electrode 11 and the second electrode 12 formedannular-like on the surface of the tray 41 are located inside of theouter circumference of the recording surface 30 of the optical recordingmedium 20 and along the outer circumference of the recording surface 30of the optical recording medium 20.

Although not shown, each of the third electrode 13 and the fourthelectrode 14 constituting the second detecting section 52 has a similarstructure to that of each of the first electrode 11 and the secondelectrode 12 and is disposed in the main body 40 of the drive so thatthe surface thereof is directed downward and it faces an opticalrecording medium 20 placed on the tray 41 when the tray 41 isaccommodated in the main body 40 of the drive.

The apparatus 50 for discriminating an optical recording medium shown inFIGS. 12 to 14 discriminates the kind of an optical recording medium 20among the optical recording media having the aforesaid differentstructures as follows.

FIG. 16 is a flow chart of a method for discriminating an opticalrecording medium using the apparatus 50 for discriminating an opticalrecording medium.

The tray 41 of the drive is discharged from the main body 40 of thedrive (Step S11) and an optical recording medium 20 is placed on theoptical recording medium setting section 41 a of the tray 41 by the user(Step S11).

As a result, a circuit shown in FIG. 7(a) is formed between the firstelectrode 11 and the second electrode 12.

Then, an alternating current signal A generated by the alternatingcurrent signal generation circuit 17 is applied to the first electrode11 under the control of the control circuit 19 while the opticalrecording medium 20 is present on the optical recording medium settingsection 41 a of the tray 41 (Step S13).

As a result, since the alternating current signal A applied to the firstelectrode 11 is transmitted to the second electrode 12 via the circuitshown in FIG. 7(a), an alternating current signal B1 appearing at thesecond electrode 12 varies depending upon the values of the capacitancecomponents C1 and C2.

The alternating current signal B1 appearing at the second electrode 12is detected by the detection circuit 18 and the control circuit 19discriminates the kind of the optical recording medium 20 placed on thetray 41 based on the alternating current signal B1 detected by thedetection circuit 18 (Step S14).

More specifically, in the case where the level of the alternatingcurrent signal B1 is equal to that obtained when the values of thecapacitance components C1 and C2 are equal to Ca, the control circuit 19discriminates that the optical recording medium 20 placed on the-tray 41is a CD type optical recording medium 20 a and in the case where thelevel of the alternating current signal B1 is equal to that obtainedwhen the values of the capacitance components C1 and C2 are equal to Cb,the control circuit 19 discriminates that the optical recording medium20 placed on the tray 41 is a DVD type optical recording medium 20 b. Onthe other hand, in the case where the level of the alternating currentsignal B1 is equal to that obtained when the values of the capacitancecomponents C1 and C2 are equal to Cc, the control circuit 19discriminates that the optical recording medium 20 placed on the tray 41is a next-generation type optical recording medium 20 c.

In this embodiment, since the first electrode 11 and the secondelectrode 12 are annular-like formed on the optical recording mediumsetting section 41 a of the tray 41 and are located inside of the outercircumference of the recording surface 30 of the optical recordingmedium 20 and along the outer circumference of the recording surface 30of the optical recording medium 20 when an optical recording medium 20is placed on the optical recording medium setting section 41 a of thetray 41, even in the case where an optical recording medium 20 to bediscriminated is warped and formed with periodical undulation in thecircumferential direction thereof, the capacitance components C1 and C2are substantially the same for the same kind of optical recording medium20 irrespective of how the optical recording medium 20 is placed on theoptical recording medium setting section 41 a of the tray 41.

Therefore, if the range of the level of the alternating current signalB1 to be obtained is obtained in advance for each kind of the opticalrecording media 20 and stored as a table 19 a in the control circuit 19,the kind of optical recording media 20 can be discriminated by referringto the table 19 a in the control circuit 19.

While the kind of an optical recording medium 20 is being discriminatedusing the first detecting section 51, the tray 41 is accommodated in themain body 40 of the drive in accordance with user's instructions (StepS15).

When the optical recording medium 20 placed on the tray 41 has reached aposition where it faces the third electrode 13 and the fourth electrode14 provided on the lower side of the second detecting section 52, acircuit shown in FIG. 7(b) is formed between the third electrode 13 andthe fourth electrode 14.

When the discrimination of the kind of the optical recording medium 20using the first detecting section 51 has been completed, an alternatingcurrent signal A generated by the alternating current signal generationcircuit 17 is applied to the third electrode 14 (Step S16).

As a result, the alternating current signal A applied to the thirdelectrode 14 is transmitted to the fourth electrode 14 via the circuitshown in FIG. 7(b) and, therefore, an alternating current signal B2appearing at the fourth electrode 14 varies depending upon the values ofthe capacitance components C3 and C4.

The alternating current signal B2 appearing at the fourth electrode 14is detected by the detection circuit 18 and the control circuit 19discriminates the kind of the optical recording medium 20 placed on thetray 41 based on the alternating current signal B2 detected by thedetection circuit 18 (Step S17).

More specifically, in the case where the level of the alternatingcurrent signal B2 is equal to that obtained when the values of thecapacitance components C3 and C4 are equal to Ca, the control circuit 19discriminates that the optical recording medium 20 placed on the tray 41is a CD type optical recording medium 20 a and in the case where thelevel of the alternating current signal B2 is equal to that obtainedwhen the values of the capacitance components C3 and C4 are equal to Cb,the control circuit 19 discriminates that the optical recording medium20 placed on the tray 41 is a DVD type optical recording medium 20 b. Onthe other hand, in the case where the level of the alternating currentsignal B2 is equal to that obtained when the values of the capacitancecomponents C3 and C4 are equal to Cc, the control circuit 19discriminates that the optical recording medium 20 placed on the tray 41is a next-generation type optical recording medium 20 c.

In this embodiment, since the third electrode 13 and the fourthelectrode 14 are annular-like formed at positions where they face anoptical recording medium 20 placed on the tray 41 accommodated in themain body 40 of the drive and are located inside of the outercircumference of the recording surface 30 of the optical recordingmedium 20 and along the outer circumference of the recording surface 30of the optical recording medium 20 when the tray 41 is accommodated inthe main body 40 of the drive, the capacitance components C3 and C4 aresubstantially the same for the same kind of optical recording medium 20irrespective of how the optical recording medium 20 is placed on theoptical recording medium setting section 41 a of the tray 41 even in thecase where an optical recording medium 20 to be discriminated is warpedand formed with periodical undulation in the circumferential directionthereof.

Therefore, if the range of the level of the alternating current signalB2 to be obtained is obtained in advance for each kind of the opticalrecording media 20 and stored as a table 19 a in the control circuit 19,the kind of optical recording media 20 can be discriminated by referringto the table 19 a in the control circuit 19.

When the discrimination of the kind of the optical recording medium 20has been completed, the optical recording medium 20 is rotated by aspindle motor (not shown) (Step S18) and a laser component and anoptical system corresponding to the kind of the optical recording medium20 discriminated at Step S6 are selected, thereby emitting a laser beam(Step S19).

Then, an initial setting operation and the like are effected similarlyto in the conventional drive and data are recorded in the opticalrecording medium 20 or data are reproduced from the optical recordingmedium 20.

Therefore, if the apparatus 50 for discriminating an optical recordingmedium according to this embodiment is mounted on a drive, it ispossible to immediately discriminate the kind of an optical recordingmedium 20 set in the drive prior to projecting a laser beam thereon.

According to this embodiment, since an optical recording medium 20 isdiscriminated using the first detecting section 51 from one side of theoptical recording medium 20 and the optical recording medium 20 isdiscriminated using the second detecting section 52 from the other sideof the optical recording medium 20, it is possible to more accuratelydiscriminate the kind of an optical recording medium 20 than in the casewhere the kind of an optical recording medium 20 is discriminated fromonly one side of an optical recording medium 20.

Further, according to this embodiment, since the first electrode 11 andthe second electrode 12 are annular-like formed on the optical recordingmedium setting section 41 a of the tray 41 and are located inside of theouter circumference of the recording surface 30 of the optical recordingmedium 20 and along the outer circumference of the recording surface 30of the optical recording medium 20 when an optical recording medium 20is placed on the optical recording medium setting section 41 a of thetray 41, the capacitance components C1 and C2 are substantially the samefor the same kind of optical recording medium 20 irrespective of how theoptical recording medium 20 is placed on the optical recording mediumsetting section 41 a of the tray 41 even in the case where an opticalrecording medium 20 to be discriminated is formed with periodicalundulation in the circumferential direction thereof. Therefore, it ispossible to accurately discriminate the kind of an optical recordingmedium 20 using the first detecting section 51 even in the case wherethe optical recording medium 20 is formed with periodical undulation inthe circumferential direction thereof.

Furthermore, according to this embodiment, since the third electrode 13and the fourth electrode 14 are annular-like formed at positions wherethey face an optical recording medium 20 placed on the tray 41accommodated in the main body 40 of the drive and are located inside ofthe outer circumference of the recording surface 30 of the opticalrecording medium 20 and along the outer circumference of the recordingsurface 30 of the optical recording medium 20 when the tray 41 isaccommodated in the main body 40 of the drive, the capacitancecomponents C3 and C4 are substantially the same for the same kind ofoptical recording medium 20 irrespective of how the optical recordingmedium 20 is placed on the optical recording medium setting section 41 aof the tray 4 even in the case where an optical recording medium 20 tobe discriminated is formed with periodical undulation in thecircumferential direction thereof, 1. Therefore, it is possible toaccurately discriminate the kind of an optical recording medium 20 usingthe second detecting section 52 even in the case where the opticalrecording medium 20 is formed with periodical undulation in thecircumferential direction thereof.

FIG. 17 is a schematic plan view showing a tray which can beaccommodated in and discharged from a main body of a drive into which anapparatus for discriminating an optical recording medium that is afurther preferred embodiment of the present invention is incorporated.

As shown in FIG. 17, the tray 41 which can be accommodated in anddischarged from the main body 40 of the drive includes an opticalrecording medium setting section 41 a on which an optical recordingmedium can be placed, and an opening 41 b formed in a central portion ofthe optical recording medium setting section 41 a and adapted forallowing a spindle motor to chuck an optical recording medium when thetray 41 is accommodated in the main body 40 of the drive.

As shown in FIG. 17, in this embodiment, a first electrode 11 and asecond electrode 12 are formed annular-like on the optical recordingmedium setting section 41 a in the vicinity of the opening 41 b. Each ofthe first electrode 11 and the second electrode 12 forms substantially ahalf of the annular portion and gaps 42 and 43 are formed between thefirst electrode 11 and the second electrode 12.

FIG. 18 is a schematic plan view showing a positional relationshipbetween an optical recording medium 20 and the first electrode 11 andthe second electrode 12 when the optical recording medium 20 is placedon the tray 41 shown in FIG. 17.

As shown in FIG. 18, when an optical recording medium 20 is placed onthe tray 41, the first electrode 11 and the second electrode 12 formedannular-like on the surface of the tray 41 are located inside of theouter circumference of the recording surface 30 of the optical recordingmedium 20 and along the outer circumference of the recording surface 30of the optical recording medium 20.

Although not shown, each of the third electrode 13 and the fourthelectrode 14 constituting the second detecting section 52 has a similarstructure to that of each of the first electrode 11 and the secondelectrode 12 and is disposed in the main body 40 of the drive so thatthe surface thereof is directed downward and it faces an opticalrecording medium 20 placed on the tray 41 when the tray 41 isaccommodated in the main body 40 of the drive.

In the apparatus for discriminating an optical recording mediumaccording to this embodiment, similarly to in the apparatus fordiscriminating an optical recording medium shown in FIGS. 12 to 14, anoptical recording medium 20 is to be discriminated is placed on theoptical recording medium setting section 41 a of the tray 41 and thekind of the optical recording medium 20 is discriminated using the firstdetecting section 51. Then, the tray 41 is accommodated in the main body40 of the drive and the kind of the optical recording medium 20 isdiscriminated using the second detecting section 52.

In this embodiment, since the first electrode 11 and the secondelectrode 12 are annular-like formed on the optical recording mediumsetting section 41 a of the tray 41 and are located inside of the outercircumference of the recording surface 30 of the optical recordingmedium 20 and along the outer circumference of the recording surface 30of the optical recording medium 20 when an optical recording medium 20is placed on the optical recording medium setting section 41 a of thetray 41, the capacitance components C1 and C2 are substantially the samefor the same kind of optical recording medium 20 irrespective of how theoptical recording medium 20 is placed on the optical recording mediumsetting section 41 a of the tray 41 even in the case where an opticalrecording medium 20 to be discriminated is warped and formed withperiodical undulation in the circumferential direction thereof.Therefore, even in the case where an optical recording medium 20 isformed with periodical undulation in the circumferential directionthereof, it is possible to accurately discriminate the kind of anoptical recording medium 20.

Further, in this embodiment, since the third electrode 13 and the fourthelectrode 14 are annular-like formed at positions where they face anoptical recording medium 20 placed on the tray 41 accommodated in themain body 40 of the drive and are located inside of the outercircumference of the recording surface 30 of the optical recordingmedium 20 and along the outer circumference of the recording surface 30of the optical recording medium 20 when the tray 41 is accommodated inthe main body 40 of the drive, the capacitance components C3 and C4 aresubstantially the same for the same kind of optical recording medium 20irrespective of how the optical recording medium 20 is placed on theoptical recording medium setting section 41 a of the tray 41 even in thecase where an optical recording medium 20 to be discriminated is formedwith periodical undulation in the circumferential direction thereof.Therefore, it is possible to accurately discriminate the kind of anoptical recording medium 20 using the second detecting section 52 evenin the case where the optical recording medium 20 is formed withperiodical undulation in the circumferential direction thereof.

FIG. 19 is a schematic plan view showing a tray which can beaccommodated in and discharged from a main body of a drive into which anapparatus for discriminating an optical recording medium that is afurther preferred embodiment of the present invention is incorporated.

As shown in FIG. 19, the tray 41 which can be accommodated in anddischarged from the main body 40 of the drive includes an opticalrecording medium setting section 41 a on which an optical recordingmedium can be placed, and an opening 41 b formed in a central portion ofthe optical recording medium setting section 41 a and adapted forallowing a spindle motor to chuck an optical recording medium when thetray 41 is accommodated in the main body 40 of the drive.

As shown in FIG. 19, a first electrode 11 and a second electrode 12 areformed annular-like over substantially the entire surface of the opticalrecording medium setting section 41 a of the tray 41. Each of the firstelectrode 11 and the second electrode 12 forms substantially a half ofthe annular portion and gaps 42 and 43 are formed between the firstelectrode 11 and the second electrode 12.

FIG. 20 is a schematic plan view showing a positional relationshipbetween an optical recording medium 20 and the first electrode 11 andthe second electrode 12 when the optical recording medium 20 is placedon the tray 41 shown in FIG. 19.

As shown in FIG. 20, when an optical recording medium 20 is placed onthe tray 41, the first electrode 11 and the second electrode 12 formedannular-like on the surface of the tray 41 are located so as to facesubstantially the entire surface of the recording surface 30 of theoptical recording medium 20.

Although not shown, each of the third electrode 13 and the fourthelectrode 14 constituting the second detecting section 52 has a similarstructure to that of each of the first electrode 11 and the secondelectrode 12 and is disposed in the main body 40 of the drive so thatthe surface thereof is directed downward and it faces substantially theentire surface of the recording surface 30 of the optical recordingmedium 20.

In the apparatus for discriminating an optical recording mediumaccording to this embodiment, similarly to in the apparatus fordiscriminating an optical recording medium shown in FIGS. 12 to 14, anoptical recording medium 20 is to be discriminated is placed on theoptical recording medium setting section 41 a of the tray 41 and thekind of the optical recording medium 20 is discriminated using the firstdetecting section 51. Then, the tray 41 is accommodated in the main body40 of the drive and the kind of the optical recording medium 20 isdiscriminated using the second detecting section 52.

In this embodiment, since the first electrode 11 and the secondelectrode 12 are annular-like formed over substantially the entiresurface of the optical recording medium setting section 41 a of the tray41 and are located so as to face substantially the entire surface of therecording surface 30 of an optical recording medium 20 when an opticalrecording medium 20 is placed on the optical recording medium settingsection 41 a of the tray 41, the capacitance components C1 and C2 aresubstantially the same for the same kind of optical recording medium 20irrespective of how the optical recording medium 20 is placed on theoptical recording medium setting section 41 a of the tray 41 even in thecase where an optical recording medium 20 to be discriminated is warpedand formed with periodical undulation in the circumferential directionthereof. Therefore, even in the case where an optical recording medium20 is formed with periodical undulation in the circumferential directionthereof, it is possible to accurately discriminate the kind of anoptical recording medium 20.

Further, in this embodiment, since the third electrode 13 and the fourthelectrode 14 are annular-like formed at positions where they face anoptical recording medium 20 placed on the tray 41 accommodated in themain body 40 of the drive and are located so as to face substantiallythe entire surface of the recording surface 30 of the optical recordingmedium 20 when the tray 41 is accommodated in the main body 40 of thedrive, the capacitance components C3 and C4 are substantially the samefor the same kind of optical recording medium 20 irrespective of how theoptical recording medium 20 is placed on the optical recording mediumsetting section 41 a of the tray 41 even in the case where an opticalrecording medium 20 to be discriminated is formed with periodicalundulation in the circumferential direction thereof. Therefore, it ispossible to accurately discriminate the kind of an optical recordingmedium 20 using the second detecting section 52 even in the case wherethe optical recording medium 20 is formed with periodical undulation inthe circumferential direction thereof.

Furthermore, the larger the areas of the first electrode 11 and secondelectrode 12 and the third electrode 13 and fourth electrode 14 are, themore accurately can the kind of an optical recording medium 20 bediscriminated even in the case where the optical recording medium 20 isformed with periodical undulation in the circumferential directionthereof. In this embodiment, since the first electrode 11 and the secondelectrode 12, the third electrode 13 and the fourth electrode 14 areformed so as to cover substantially the entire surface of the recordingsurface 30 of an optical recording medium 20, it is possible toaccurately discriminate the kind of an optical recording medium 20.

FIG. 21 is a schematic plan view showing a tray which can beaccommodated in and discharged from a main body of a drive into which anapparatus for discriminating an optical recording medium that is afurther preferred embodiment of the present invention is incorporated.

As shown in FIG. 21, the tray 41 which can be accommodated in anddischarged from the main body 40 of the drive includes an opticalrecording medium setting section 41 a on which an optical recordingmedium can be placed, and an opening 41 b formed in a central portion ofthe optical recording medium setting section 41 a and adapted forallowing a spindle motor to chuck an optical recording medium when thetray 41 is accommodated in the main body 40 of the drive.

As shown in FIG. 21, in this embodiment, a first electrode 11 isannular-like formed on the optical recording medium setting section 41 ain the vicinity of the opening 41 b and a second electrode 12 isannular-like formed on the optical recording medium setting section 41 ain the vicinity of a shoulder portion 44.

FIG. 22 is a schematic plan view showing a positional relationshipbetween an optical recording medium 20 and the first electrode 11 andthe second electrode 12 when the optical recording medium 20 is placedon the tray 41 shown in FIG. 21.

As shown in FIG. 22, when an optical recording medium 20 is placed onthe tray 41, the first electrode 11 formed annular-like on the surfaceof the tray 41 is located outside of the inner circumference of therecording surface 30 of the optical recording medium 20 and along theinner circumference of the recording surface 30 of the optical recordingmedium 20 and the second electrode 12 formed annular-like on the surfaceof the tray 41 is located inside of the outer circumference of therecording surface 30 of the optical recording medium 20 and along theouter circumference of the recording surface 30 of the optical recordingmedium 20.

Although not shown, the third electrode 13 and the fourth electrode 14constituting the second detecting section 52 are constituted so as toform two concentric annular portions similarly to the first electrode 11and the second electrode 12 and are disposed in the main body 40 of thedrive so that the surfaces thereof are directed downward and they facean optical recording medium 20 placed on the tray 41 when the tray 41 isaccommodated in the main body 40 of the drive.

In the apparatus for discriminating an optical recording mediumaccording to this embodiment, similarly to in the apparatus fordiscriminating an optical recording medium shown in FIGS. 12 to 14, anoptical recording medium 20 is to be discriminated is placed on theoptical recording medium setting section 41 a of the tray 41 and thekind of the optical recording medium 20 is discriminated using the firstdetecting section 51. Then, the tray 41 is accommodated in the main body40 of the drive and the kind of the optical recording medium 20 isdiscriminated using the second detecting section 52.

In this embodiment, the first electrode 11 is annular-like formed on theoptical recording medium setting section 41 a in the vicinity of theopening 41 b and the second electrode 12 is annular-like formed on theoptical recording medium setting section 41 a in the vicinity of theshoulder portion 44 so that when an optical recording medium 20 isplaced on the tray 41, the first electrode 11 formed annular-like on thesurface of the tray 41 is located outside of the inner circumference ofthe recording surface 30 of the optical recording medium 20 and alongthe inner circumference of the recording surface 30 of the opticalrecording medium 20 and the second electrode 12 formed annular-like onthe surface of the tray 41 is located inside of the outer circumferenceof the recording surface 30 of the optical recording medium 20 and alongthe outer circumference of the recording surface 30 of the opticalrecording medium 20. Therefore, even in the case where an opticalrecording medium 20 to be discriminated is warped and formed withperiodical undulation in the circumferential direction thereof, thecapacitance components C1 and C2 are substantially the same for the samekind of optical recording medium 20 irrespective of how the opticalrecording medium 20 is placed on the optical recording medium settingsection 41 a of the tray 41. Accordingly, even in the case where anoptical recording medium 20 is formed with periodical undulation in thecircumferential direction thereof, it is possible to accuratelydiscriminate the kind of an optical recording medium 20.

Further, in this embodiment, the third electrode 13 and the fourthelectrode 14 are disposed so as to face an optical recording medium 20placed on the tray 41 accommodated in the main body 40 of the drive andto form two concentric annular portions in such a manner that when anoptical recording medium 20 is placed on the tray 41, the thirdelectrode 13 is located outside of the inner circumference of therecording surface 30 of the optical recording medium 20 and along theinner circumference of the recording surface 30 of the optical recordingmedium 20 and the second electrode 12 is located inside of the outercircumference of the recording surface 30 of the optical recordingmedium 20 and along the outer circumference of the recording surface 30of the optical recording medium 20. Accordingly, even in the case wherean optical recording medium 20 to be discriminated is formed withperiodical undulation in the circumferential direction thereof, thecapacitance components C3 and C4 are substantially the same for the samekind of optical recording medium 20 irrespective of how the opticalrecording medium 20 is placed on the optical recording medium settingsection 41 a of the tray 41. Therefore, it is possible to accuratelydiscriminate the kind of an optical recording medium 20 using the seconddetecting section 52 even in the case the optical recording medium 20 isformed with periodical undulation in the circumferential directionthereof.

FIG. 23 is a schematic plan view showing a tray which can beaccommodated in and discharged from a main body of a drive into which anapparatus for discriminating an optical recording medium that is afurther preferred embodiment of the present invention is incorporatedand on which a spindle motor is mounted.

As shown in FIG. 23, in this embodiment, the tray 45 is constituted insuch a manner that the user causes a spindle motor 46 to directly chuckan optical recording medium 20. Trays constituted in the manner of thetray 45 are widely used in note-type personal computers.

As shown in FIG. 23, an optical system 47 for emitting a laser beam ishoused in the tray 45 and the tray 45 is formed with an optical systemmovable region 48 so that the optical system 47 can be moved in a radialdirection of an optical recording medium 20 when data are recorded inthe optical recording medium 20 chucked by the spindle motor 46 or whendata are reproduced from an optical recording medium 20.

As shown in FIG. 23, in this embodiment, a first electrode 11 and asecond electrode 12 are annular-like formed along the outercircumference of an optical recording medium setting section 45 a of thetray 45. Each of the first electrode 11 and the second electrode 12forms substantially a half of the annular portion and the optical systemmovable region 48 and a gap 49 is formed between the first electrode 11and the second electrode 12.

In this embodiment, when an optical recording medium 20 is placed on thetray 45, the first electrode 11 and the second electrode 12 annular-likeformed on the surface of the tray 45 are located along the outercircumference of the recording surface 30 of the optical recordingmedium 20.

In this embodiment, the first electrode 11 and the second electrode 12are annular-like disposed along the outer circumference of an opticalrecording medium setting section 45 a of the tray 45 and when an opticalrecording medium 20 is placed on the tray 45, the first electrode 11 andthe second electrode 12 annular-like formed on the surface of the tray45 are located along the outer circumference of the recording surface 30of the optical recording medium 20. Therefore, even in the case where anoptical recording medium 20 to be discriminated is warped and formedwith periodical undulation in the circumferential direction thereof, thecapacitance components C1 and C2 are substantially the same for the samekind of optical recording medium 20 irrespective of how the opticalrecording medium 20 is placed on the optical recording medium settingsection 45 a of the tray 45. Hence, even in the case where an opticalrecording medium 20 is formed with periodical undulation in thecircumferential direction thereof, it is possible to accuratelydiscriminate the kind of an optical recording medium 20.

FIG. 24 is a schematic cross-sectional view showing the state where anoptical recording medium is placed on a tray, wherein FIG. 24 (a) showsthe case where an optical recording medium formed with no periodicalundulation in the circumferential direction thereof is placed on thetray and FIGS. 24(b) and(c) shows the cases where an optical recordingmedium formed with a periodical undulation in the circumferentialdirection thereof is placed on the tray.

As shown in FIG. 24(a), when an optical recording medium formed with noperiodical undulation in the circumferential direction thereof is placedon a tray 41, the distances D1 between a first electrode 11 and a secondelectrode 12 and the surface of the optical recording medium 20 areconstant.

To the contrary, as shown in each of FIG. 24(b) and FIG. 24(c), when anoptical recording medium 20 formed with periodical undulation in thecircumferential direction thereof is placed on the tray 41, thedistances between a first electrode 11 and a second electrode 12 and thesurface of the optical recording medium 20 vary between the minimumdistance D2 and the maximum distance D3 depending upon the position inthe circumference direction of the optical recording medium 20 and asperiodical undulation in the circumferential direction the opticalrecording medium 20 becomes large, the difference ΔD between the maximumdistance D3 and the minimum distance D2 becomes large.

Therefore, it is preferable to set the value the distance D1 to be equalto the height of a shoulder portion 44 and determine areas and positionsof the first electrode 11 and the second electrode 12 in relation to theminimum distance D2, the maximum distance D3 and the difference ΔDbetween the maximum distance D3 and the minimum distance D2 when eachkind of an optical recording medium 20 is formed with the maximumundulation allowed by the standard so that the kind of an opticalrecording medium 20 can be accurately discriminated even in the casewhere each kind of an optical recording medium is formed with themaximum undulation allowed by the standard.

The present invention has thus been shown and described with referenceto specific embodiments. However, it should be noted that the presentinvention is in no way limited to the details of the describedarrangements but changes and modifications may be made without departingfrom the scope of the appended claims.

For example, in the above described embodiments, although opticalrecording media in which focus distances are different from each otherare discriminated, the present invention can be applied to the casewhere a plurality kinds of optical recording media for which a commonrecording and reproducing system is used, for example, a DVD in whichdata are to be recorded in one layer on one side and a DVD in which dataare to be recorded in two layers on one side, are discriminated.

Further, in the embodiments shown in FIGS. 3 and 8, although the firstdetecting section 31 and the second detecting section 32 are provided inthe main body 40 of the drive, it is not absolutely necessary to providethe first detecting section 31 and the second detecting section 32 inthe main body 40 of the drive and one of them may be provide on the tray41.

Furthermore, in the embodiments shown in FIGS. 3, 8 and 9, although thealternating current signal A is applied to the first electrode 11 andthe third electrode 13 while the first detecting section 31 and thesecond detecting section 32 are in contact with the light incidenceplane of an optical recording medium 20, thereby discriminating the kindof an optical recording medium 20, it is not absolutely necessary toapply the alternating current signal A is applied to the first electrode11 and the third electrode 13 while the first detecting section 31 andthe second detecting section 32 are in contact with the light incidenceplane of an optical recording medium 20 and to discriminate the kind ofan optical recording medium 20 and it is possible to apply analternating current signal A to the first electrode 11 and the thirdelectrode 13 while the first detecting section 31 and the seconddetecting section 32 are located close to the light incidence plane ofan optical recording medium 20 and to discriminate the kind of anoptical recording medium 20. In such a case, since the discriminationaccuracy of an optical recording medium 20 is affected by the warpageand periodical circumferential undulation of an optical recording medium20, it is preferable to constitute a first electrode 11 and a secondelectrode 12, and a third electrode 13 and a fourth electrode 14 so asto have structures shown in FIGS. 14, 17, 19 and 21.

Moreover, in the embodiment shown in FIG. 21, although the firstelectrode 11 is annular-like formed on the optical recording mediumsetting section 41 a in the vicinity of the opening 41 b and the secondelectrode 12 is annular-like formed on the optical recording mediumsetting section 41 a in the vicinity of a shoulder portion 44, it ispossible to annular-like form the second electrode 12 on the opticalrecording medium setting section 41 a in the vicinity of the opening 41b and annular-like form the first electrode 11 on the optical recordingmedium setting section 41 a in the vicinity of a shoulder portion 44.

Further, in the embodiment shown in FIG. 21, although the firstelectrode 11 and the second electrode 12 are disposed to be spaced fromeach other in a radial direction of the optical recording medium andover substantially 360 degrees around the center of the tray 41, it isnot absolutely necessary to dispose the first electrode 11 and thesecond electrode 12 over substantially 360 degrees around the center ofthe tray 41 and it is sufficient for the first electrode 11 and thesecond electrode 12 to be disposed over substantially 180 degrees aroundthe center of the tray 41. Preferably, the first electrode 11 and thesecond electrode 12 are disposed over an angle equal to or larger thansubstantially 270 degrees around the center of the tray 41.

Furthermore, in the embodiment shown in FIG. 23, although the firstelectrode 11 and the second electrode 12 are annular-like formed alongthe outer circumference of the optical recording medium setting section45a of the tray 45, it is possible to form the first electrode 11 andthe second electrode 12 in the vicinity of and along the innercircumference of the optical recording medium setting section 45 a ofthe tray 45 or to form the first electrode 11 and the second electrode12 over substantially the entire surface of the optical recording mediumsetting section 45 a of the tray 45. Further, it is possible to providethe first electrode 11 and the second electrode 12 on the tray 41 at aportion corresponding to the vicinity of the inner circumference of therecording surface 30 of an optical recording medium 20 or to form thesecond electrode 12 and the first electrode 11 on the tray 41 at aportion corresponding to the vicinity of the outer circumference of therecording surface 30 of an optical recording medium 20. In the casewhere the first electrode 11 and the second electrode 12 are provided ona tray 45 widely used for note-type personal computers or the like, ifspace required for disposing the first electrode 11 and the secondelectrode 12 is restricted, it is preferable to provide the firstelectrode 11 and the second electrode 12 in the vicinity of and alongthe inner circumference of the optical recording medium setting section45 a of the tray 45.

Moreover, in the embodiments shown in FIGS. 14, 17 and 19, although thefirst electrode 11 and the second electrode 12 are formed oversubstantially 180 degrees around the center of the tray 41, it is notabsolutely necessary to form the first electrode 11 and the secondelectrode 12 over substantially 180 degrees around the center of thetray 41 and the first electrode 11 and the second electrode 12 may beformed at symmetrical positions with respect to a straight line passingthrough the center of the tray 41 so that each of them is formed over anangle equal to or larger than 90 degrees.

Further, in the embodiments shown in FIGS. 14, 17, 19, 21 and 23,although each of the first electrode 11 and the second electrode 12 isannular-like formed on the tray 41, 45, it is not absolutely necessaryto accurately annular-like form each of the first electrode 11 and thesecond electrode 12 and it is sufficient for each of the first electrode11 and the second electrode 12 to be formed substantially annular-like.

Furthermore, in the embodiments shown in FIGS. 14, 17, 19 and 21,although the third electrode 13 and the fourth electrode 14 provided inthe main body 40 of the drive have similar structures to those of thefirst electrode 11 and the second electrode 1-2 provided on the tray 41,it is not absolutely necessary for the third electrode 13 and the fourthelectrode 14 to have similar structures to those of the first electrode11 and the second electrode 12 and it is possible to provide the thirdelectrode 13 and the fourth electrode 14 so as to have the structuresshown in FIGS. 14, 17 and 21 while the first electrode 11 and the secondelectrode 12 have the structures shown in FIG. 14, for example.

Moreover, in the above described embodiments, although the kind of anoptical recording medium 20 is discriminated by employing the firstelectrode 11 and the second electrode 12 and detecting the alternatingcurrent signal B1 appearing at the second electrode 12 when thealternating current signal A is applied to the first electrode 11, andthe kind of an optical recording medium 20 is separately discriminatedby employing the third electrode 13 and the fourth electrode 14 anddetecting the alternating current signal B2 appearing at the fourthelectrode 14 when the alternating current signal A is applied to thethird electrode 13, it is possible to discriminate the kind of anoptical recording medium 20 by employing a planar-coil like electrodeand detecting an eddy current generated by supplying an electricalcurrent to the planar-coil like electrode.

According to the present invention, it is possible to provide anapparatus for discriminating an optical recording medium and a methodfor discriminating an optical recording medium which can reliablydiscriminate the kind of an optical recording medium.

Further, according to the present invention, it is possible to providean apparatus for discriminating an optical recording medium and a methodfor discriminating an optical recording medium which can reliablydiscriminate the kind of an optical recording medium even in the casewhere the optical recording medium to be discriminated is warped andformed with periodical undulation in the circumferential directionthereof.

Furthermore, according to the present invention, it is possible toprovide an apparatus for discriminating an optical recording medium anda method for discriminating an optical recording medium constituted soas to be irradiated with a laser beam from a side opposite to asubstrate, which can reliably discriminate the kind of an opticalrecording medium.

1. An apparatus for discriminating an optical recording mediumcomprising at least a first dielectric layer, a second dielectric layerand a conductive layer formed between the first dielectric layer and thesecond dielectric layer, the apparatus for discriminating an opticalrecording medium comprising a first detecting section provided with anelectrode and disposable in the vicinity of a surface of the firstdielectric layer, a second detecting section provided with an electrodeand disposable in the vicinity of a surface of the second dielectriclayer and a signal applying means for applying a signal for detection tothe electrode of the first detecting section and the electrode of thesecond detecting section.
 2. An apparatus for discriminating an opticalrecording medium in accordance with claim 1, which further comprises adriving means for moving the first detection section to a position inthe vicinity of the surface of the first dielectric layer and away fromthe surface of the first dielectric layer and moving the seconddetection section to a position in the vicinity of the surface of thesecond dielectric layer and away from the surface of the seconddielectric layer, the driving means being constituted so as to locatethe first detecting section and the second detecting section atpositions in the vicinity of the surfaces of the first dielectric layerand the second dielectric layer where the first detecting section andthe second detecting section do not face each other.
 3. An apparatus fordiscriminating an optical recording medium in accordance with claim 2,wherein the driving means is constituted so as to simultaneously locatethe first detecting section and the second detecting section atpositions in the vicinity of the surfaces of the first dielectric layerand the second dielectric layer and the signal applying means isconstituted so as to simultaneously apply signals for detection to theelectrode of the first detecting section and the electrode of the seconddetecting section.
 4. An apparatus for discriminating an opticalrecording medium in accordance with claim 2, wherein the driving meansincludes a first driving means for moving the first detection section toa position in the vicinity of the surface of the first dielectric layerand away from the surface of the first dielectric layer and a seconddriving means for moving the second detection section to a position inthe vicinity of the surface of the second dielectric layer and away fromthe surface of the second dielectric layer.
 5. An apparatus fordiscriminating an optical recording medium in accordance with claim 1,which further comprises a driving means for moving the first detectionsection to a position in the vicinity of the surface of the firstdielectric layer and away from the surface of the first dielectric layerand moving the second detection section to a position in the vicinity ofthe surface of the second dielectric layer and away from the surface ofthe second dielectric layer, the driving means being constituted so asto locate the first detecting section and the second detecting sectionat positions in the vicinity of the surfaces of the first dielectriclayer and the second dielectric layer where the first detecting sectionand the second detecting section face each other.
 6. An apparatus fordiscriminating an optical recording medium in accordance with claim 5,wherein the driving means is constituted so as to move one of the firstdetecting section and the second detecting section to a position in thevicinity of one of the first dielectric layer and the second dielectriclayer while keeping the other of the first detecting section and thesecond detecting section away from the other of the first dielectriclayer and the second dielectric layer and the signal applying means isconstituted so as to selectively apply a signal for detection to one ofthe electrode of the first detecting section and the electrode of thesecond detecting section.
 7. An apparatus for discriminating an opticalrecording medium in accordance with claim 5, wherein the driving meansis constituted as a single driving means.
 8. An apparatus fordiscriminating an optical recording medium in accordance with claim 1,wherein the driving means is constituted so as to bring the firstdetecting section into contact with the surface of the first dielectriclayer and bring the second detecting section into contact with thesurface of the second dielectric layer.
 9. An apparatus fordiscriminating an optical recording medium in accordance with claim 1,wherein at least one of the first detecting section and the seconddetecting section is disposed on a tray of a drive.
 10. An apparatus fordiscriminating an optical recording medium in accordance with claim 9,wherein at least one of the electrode of the first detecting section andthe electrode of the second detecting section is disposed around acenter of a tray of a drive on which the optical recording medium is tobe placed over substantially 180 degrees.
 11. An apparatus fordiscriminating an optical recording medium in accordance with claim 10,wherein at least one of the electrode of the first detecting section andthe electrode of the second detecting section includes a first electrodeto which a signal for detection is applied and a second electrode atwhich a signal depending upon the kind of an optical recording mediumappears in response to application of the signal for detection to thefirst electrode.
 12. An apparatus for discriminating an opticalrecording medium in accordance with claim 11, wherein the firstelectrode and the second electrode are disposed to be spaced from eachother and to form at least a part of a substantially annular portionaround the center of the tray.
 13. An apparatus for discriminating anoptical recording medium in accordance with claim 12, wherein the firstelectrode and the second electrode are disposed to be spaced from eachother in a circumferential direction of the optical recording medium tobe placed on the tray and over substantially 180 degrees around thecenter of the tray.
 14. An apparatus for discriminating an opticalrecording medium in accordance with claim 12, wherein the firstelectrode and the second electrode are disposed to be spaced from eachother in a radial direction of the optical recording medium to be placedon the tray and over substantially 180 degrees around the center of thetray.
 15. An apparatus for discriminating an optical recording medium inaccordance with claim 14, wherein the first electrode and the secondelectrode are disposed to be spaced from each other in a radialdirection of the optical recording medium to be placed on the tray andover substantially 360 degrees around the center of the tray.
 16. Anapparatus for discriminating an optical recording medium in accordancewith claim 1, wherein at least one of the first detecting section andthe second detecting section is disposed in a main body of a drive. 17.An apparatus for discriminating an optical recording medium inaccordance with claim 16, wherein at least one of the first detectingsection and the second detecting section is constituted by a shaft of aroller of a slot-loading mechanism.
 18. A method for discriminating anoptical recording medium comprising at least a first dielectric layer, asecond dielectric layer and a conductive layer formed between the firstdielectric layer and the second dielectric layer, the method fordiscriminating an optical recording medium comprising steps of locatinga first detecting section provided with an electrode in the vicinity ofa surface of the first dielectric layer, applying a signal for detectionto the electrode of the first detecting section, locating a seconddetecting section provided with an electrode in the vicinity of asurface of the second dielectric layer, and applying a signal fordetection to the electrode of the second detecting section, therebydiscriminating the kind of the optical recording medium.